記述言語：英語   掲載種別：研究論文（学術雑誌）  

©2018 The Ceramic Society of Japan. All rights reserved. Microwave heating is known to provide extremely rapid synthesis of silicon carbide (SiC) from mixtures of silicon and carbon powders. The formation mechanism has long been considered to be a solid-state reaction among the powders in the mixture. Here, we present a new reaction mechanism via a gas-phase route. We have confirmed successful synthesis of -SiC powder by microwave-heating of a small amount of Si powder that was entered into a quartz tube and then embedded in graphite powder, although no direct contact between the Si and graphite powders was allowed. Scanning electron microscopy observations revealed that the -SiC powder was formed by direct carbonization of the Si powder. Since the atmosphere during the reaction comprises a vast majority of carbon monoxide (CO) gas according to the Boudouard equilibrium, the carbonization appears to have taken place via the CO gas. The contribution of such a gas-phase reaction could account in part for the rapidity of the microwave-heating reactions reported so far, which can hardly be explained solely by solid-state reactions among the mixed powders.

DOI： 10.2109/jcersj2.18121

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Ceramic Society of Japan  

This report presents a new route to fabricating a ferrite-based magnetic nanocomposite consisting of a ferromagnetic metal (α-Fe) and a ferrimagnetic spinel ferrite (Fe3O4). The process is based on the eutectoid decomposition of FeO, leading to the formation of a lamellar nanostructure of α-Fe and Fe3O4. A sandwiched nanostructure of this type is preferable for exchange coupling between adjacent lamellae, because each lamella is subjected to exchange coupling via either side of the interface. It was found that decomposition of FeO takes place preferentially in the temperature range of 723-773K, in which the decomposition is almost fully completed within 10 h. The room-temperature magnetization measurements gave rise to a high saturation magnetization above 100 emu/g, which is larger than that of single-phase Fe3O4. Since a smooth magnetization curve with single-phaselike behavior was observed despite the coexistence of two magnetic phases, the two phases could be magnetically exchange-coupled. Due to the ease of tuning the magnetic properties of the spinel ferrites with the substitution of constituent metal ions, the fabrication process described here could represent a potential route to making a variety of iron-based metal/ferrite magnetic nanocomposites.

DOI： 10.2109/jcersj2.17237

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

Dipolar ferromagnetism formed in Fe3O4 nanoparticle arrays is revealed by Fresnel Lorentz microscopy and electron holography. Dipolar domain walls do not lie preferentially along macrograin boundaries but depend on the overall shape of the assembly, meaning magnetostatic energy dominates. The domain structures are imaged at different temperatures for both monolayer and bilayer arrays. The domain wall contrast in the monolayer region is visible until 575 degrees C, and the magnetic order parameter steeply drops toward the temperature. In the bilayer region, finer and more complicated domains are formed. (C) 2011 American Institute of Physics. [doi:10.1063/1.3556562]

DOI： 10.1063/1.3556562

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IOP PUBLISHING LTD  

Iron-coated Nd-Fe-B composite powder was prepared by thermal decomposition of iron pentacarbonyl in an inert organic solvent in the presence of alkylamine. Though this method is based on a modified solution-phase process to synthesize highly size-controlled iron nanoparticles, it is in turn featured by a suppressed formation of iron nanoparticles to achieve an efficient iron coating solely onto the surfaces of rare-earth magnet powder. The Nd-Fe-B magnetic powder was successfully coated by iron shells whose thicknesses were of the order of submicrometer to micrometer, being tuneable by the amount of initially loaded iron pentacarbonyl in a reaction flask. The amount of the coated iron reached to more than 10 wt.% of the initial Nd-Fe-B magnetic powder, which is practically sufficient to fabricate Nd-Fe-B/alpha-Fe nanocomposite permanent magnets.

DOI： 10.1088/1742-6596/266/1/012050

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記述言語：日本語  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本金属学会  

DOI： 10.2320/jinstmet.73.135

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SCIENCE PRESS  

The brookite-phase TiO{in2} was prepared by a hydrothermal synthesis of titanium chloride solution. The thermolysis time and the pH value of the solution were controlled during the synthesis. X-ray diffraction experiments showed that TiO{in2} powders partially containing the brookite-phase were successfully obtained. A great amount of OH{su\t-} in the reaction solution was found to be important to obtain the brookite phase because the intermediate complex leading to the brookite phase consumes more OH{su\t-} than other phases like the rutile. © 2009 Science in China Press and Springer-Verlag GmbH.

DOI： 10.1007/s11431-009-0024-5

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

The brookile-phase TiO2 was prepared by a hydrothermal synthesis of titanium chloride solution. The thermolysis time and the pH value of the solution were controlled during the synthesis. X-ray diffraction experiments showed that TiO2 powders partially containing the brookite-phase were successfully obtained. A higher amount of OH- in file reaction solution was found to be important to obtain the brookite phase because the intermediate complex leading to the brookite phase consumes more amount of OH- than other phases like the rutile.

DOI： 10.4028/www.scientific.net/MSF.610-613.285

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記述言語：日本語   出版者・発行元：日本材料科学会  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

Electron holography has revealed dipolar ferromagnetic domain structures in ordered monolayer arrays of Co nanoparticles. In zero-field-cooling experiments, we demonstrate the formation of micron-sized magnetically ordered regions with transverse domain walls, and a spatially varying moment order parameter. Truncated vortex structures that can be modified by an applied field are observed near the sample edges. The collectively magnetized state shows soft magnetic properties and long-range order that is stable over times over 1 h at 108 K. (C) 2008 American Institute of Physics.

DOI： 10.1063/1.2973675

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

The simple cubic packing rarely appears in nature primarily due to its low packing density. Here, we present that the cubic particle shape induces a preferred formation of three-dimensional arrays of simple cubic arrangement, confirmed by transmission electron microscopy and small-angle x-ray scattering. The calculation of van der Waals interaction energy between the particle cores showed that the highly coordinated, simple cubic packing is energetically the most stable, being consistent with the present experimental result. (C) 2008 American Institute of Physics.

DOI： 10.1063/1.2887902

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOC APPLIED PHYSICS  

Monodispersed Fe-Ti-O nanoparticles and Fe-O nanoparticles were prepared by liquid-phase synthesis to be used as catalysts for carbon nanotube (CNT) growth. Vertically aligned, dense CNTs were obtained in the case of Fe-Ti-O nanoparticles, whereas few CNTs were grown when Fe-O particles were used. CNTs with a diameter of 4.3 +/- 0.7 mn were grown from Fe-10 at. % Ti nanoparticles with a diameter of 3.8 +/- 0.6 nm. These CNTs mainly consist of double- and triple-walled CNTs. The catalytic activity of nanoparticles peaks at around 20-25 at.% Ti. The diameter controllability of Fe-20 at.% Ti nanoparticles was lower than that of Fe-10 at. % Ti nanoparticles, although a 200-mu m-thick CNT forest was grown within 10 min. The energy-dispersive X-ray spectroscopy (EDS) analysis of the Fe-Ti-O nanoparticles before and after CNT growth revealed the depletion of Ti in the nanoparticles during the CNT growth, indicating the extraction of Ti from the nanoparticles.

DOI： 10.1143/JJAP.46.3700

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

The formation of large-scale ferromagnetic domains has been detected in quasi-three-dimensional random assemblies of monodisperse 6 nm Co/CoO core-shell clusters by electron holography. This is primarily attributed to the magnetic dipole interactions between these clusters, because the exchange coupling between neighboring Co cores is effectively interrupted by antiferromagnetic CoO surface layers. The magnetic field-cooled effect has been also detected by in-situ electron microscope experiment. The field-induced alignment of magnetic moments during the cooling experiment is ascribable to the exchange interactions between Co cores and CoO shells. (c) 2007 American Institute of Physics.

DOI： 10.1063/1.2748077

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

Monodispersed Fe-V-O nanoparticles were prepared by a liquid-phase synthesis to be used as catalysts for carbon nanotube (CNT) growth. Vertically aligned, dense CNTs have been grown from the highly active Fe-V-O nanoparticles by chemical vapor deposition. Diameter distribution of CNTs (3.7 +/- 0.6 nm) was consistent with that of the original nanoparticles (3.1 +/- 0.5 nm), and the value was smaller than those of other reported vertically aligned CNTs from as-prepared nanoparticles. TEM study showed that the CNTs consisted mainly of double-walled CNTs (single: 14%, double: 74%, and triple: 12%). The CNT diameter increased to 4.4 +/- 0.8 nm as the growth temperature was increased from 810 to 870 degrees C. Energy dispersive X-ray spectroscopy of nanoparticles before and after the CNT growth revealed that the V content decreased from 7.2 to 2.7 at.%, suggesting that the segregation of Fe and V played an important role for the high activity of the Fe-V-O nanoparticles. (C) 2007 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.carbon.2007.02.016

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

We synthesized iron nanoparticles, 15-20 nm in size, having saturation magnetization, M-s, of 170 emu/g. They were embedded in copolymer beads of styrene (St) and glycidyl methacrylate (GMA), which were coated with poly-GMA by seed polymerization. The resultant Fe/St-GMA/GMA beads had diameters of 100-200 nm and M-s of 60 emu/g. By coating with poly-GMA, the zeta potential of the beads changed from -93.7 to -54.8 mV, as measured by an electrophoresis method. This facilitated (as revealed by gel electrophoresis method) nonspecific protein adsorption suppression, a requisite for nanoparticles to be applied to carriers for bioscreening. (C) 2006 American Institute of Physics.

DOI： 10.1063/1.2165127

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Simple calculations of potential energy were made to account for the preferred appearance of square arrays in cubic nanoparticle self-assemblies, taking into account the van der Waals attractions between the particles. The results showed that the nearest neighbor particles have a dominant contribution to the potential energy, and hence, play a decisive role to determine the lattice symmetry of the resulting arrays. From comparative studies between two close-packed arrangements (a square array and a pseudo-hexagonal array), it was found that the highly coordinated square array is energetically more stable than the lowly coordinated pseudo-hexagonal one, (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2005.10.111

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記述言語：日本語   出版者・発行元：The Japan Institute of Metals and Materials  

DOI： 10.2320/materia.44.680

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

We have investigated the size-evolution process of ZnS NCs using the MALDI-TOFMS instrument. The size estimations obtained by MALDI-TOFMS are relatively in good agreement with those by UV-vis spectroscopy and transmission electron microscope. MALDI-TOFMS elucidates the thermodynamically stable sizes and unique size-evolution process of ZnS NCs. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2005.03.114

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL INST MATERIALS SCIENCE  

In this paper report on the synthesis of copper and zinc sulfide nanocrystals (NCs) via the formation of polymetallic thiolate cages. Cu2S NCs derived from Cu-dodecanethiol complex formed well-defined spherers, which were sufficiently monodisperse (with a size distribution of similar to 10% standard deviation of approximately 4.7 nm diameter on average) to generate ordered self-assemblies. An electron diffraction pattern and UV-vis spectrum of Cu2S NCs indicate that this process can provide pure beta-chalcocite (Cu2S). Nearly monodisperse ZnS NCs with a size ranging from 3 to 7 nm were obtained by thermolysis of the S-Zn-dodecanethiol precursor. The electron diffraction pattern indicates that zinc sulfide NCs are either wurtzite or a mixture of wurtzite and zincblende. TEM observation and UV-vis spectra revealed that the growth rate of ZnS NCs depends strongly on the annealing temperature. UV-vis spectra of 3 nm ZnS NCs show sharp excitonic features and a large blue shift from the bulk material. The photoluminescence spectra exhibit a large red shift from the absorption band edges. These shifts could be attributed to recombination from the surface traps. The narrow size distribution of Cu2S and ZnS NCs led to the formation of ordered self-assemblies with various well-defined but nonclosed-packing. (c) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.stam.2004.08.005

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Self-assembled arrays of iron nanoparticles are characterized structurally by transmission electron microscopy and small-angle X-ray scattering, and magnetically by low-temperature hysteresis loops and magnetic relaxation. The differences in the magnetic properties are related to the strength of magnetic dipolar interactions and to the degree of structural ordering in the arrays. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2004.04.025

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN INST METALS  

We report synthesis of zinc sulfide nanocrystals (NCs) via formation of polymetallic thiolate cages. Nearly monodisperse ZnS NCs with size ranging from 2.2 to 7 nm were obtained by thermolysis of S-Zn-dodecanethiol precursors. The electron diffraction pattern of zinc sulfide NCs indicates that precipitates are wurtzite or mixture of wurtzite and zincblende. TEM observation and UV-vis spectra reveal that the growth rate of ZnS NCs considerably depends on the annealing temperature. UV-vis spectra of ZnS NCs with size smaller than 3 nm show sharp excitonic features and a large blue shift from the bulk material. The photoluminescence spectra exhibit large red shift from the absorption band edges, being attributed to electron-hole recombination by surface traps. The narrow size distribution of ZnS NCs leads to formation of ordered self-assemblies with various well-defined structures, where non-closed-packing structure is predominant.

DOI： 10.2320/matertrans.45.2650

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：INST PURE APPLIED PHYSICS  

Highly monodisperse, metallic iron nanoparticles were prepared by the alcohol reduction of a nontoxic metal precursor (Fe(III) acetylacetonate) in an organic solvent at elevated temperatures. In order to obtain a metallic iron phase and minimize iron oxide ones, a relatively high molar ratio of the reducing agent to the precursor is required. Compared with a single-step reaction, a two-step seed-mediated synthesis results in the systematic control of particle diameter while maintaining monodispersity. The standard deviation of particle diameter is less than 10%, which is sufficiently small to lead to ordered self-assemblies.

DOI： 10.1143/jjap.43.4458

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掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：CHEMICAL SOC JAPAN  

We report a novel water-free processing of monodisperse and pure Cu2S nanocrystals (NCs) by thermolysis of copper-dodecanethiol complex. The narrow size distribution led to the formation of ordered self-assemblies with various well-defined structures. However, unclose-packing structure was observed as a predominant phase.

DOI： 10.1246/cl.2004.352

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：WILEY-V C H VERLAG GMBH  

Nearly monodispersed oxide-coated Fe cluster assemblies were prepared using a plasma-gas-condensation style cluster beam deposition apparatus (D. L. Peng et al. J. Appl. Phys. 92 3075 (2002)). The characterization of such assemblies is presented using SQUID magnetometry. The aim of this contribution is the interpretation of the initial magnetization curves instead of the usual presentation of hysteresis loops and coercivities. The description of the initial magnetization is based on a proposed vector model valid for Stoner-Wohlfarth particles. The model includes the particles' anisotropy and possible interactions regarding these influences as equivalent magnetic fields. The model is an extension of the one described by Michele et al. (J. Phys.: Condens. Matter 16 427 (2004)) regarding the fact that in a completely demagnetized state, in the sample consisting of a very large number of particles always equal anisotropy fields of opposite signs are present. We measured the initial magnetization curves for different temperatures and present the temperature dependence of the model's parameters. (C) 2004 WILEYNCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssc.200405513

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

We describe the magnetic properties of gold-coated iron nanoparticles, and the effects of low pH and heat treatment. Acicular iron and spherical iron based nanoparticles were coated with a thin layer of gold. The morphology and magnetic properties of magnetic particles were examined using transmission electron microscopy and alternative gradient magnetometry. While the small spherical particles had relatively uniform layers coatings, the larger acicular particles had many gold clusters decorating the surface. The original acicular iron nanoparticles had a specific magnetic moment of 145 emu/g and a coercivity of 1664 Oe. Corrosion tests showed good corrosion resistance for gold-coated commercial iron particles even in a 1.0x10(-3) M HCl solution at 80degreesC for 12 h, compared with uncoated particles. (C) 2003 American Institute of Physics.

DOI： 10.1063/1.1555312

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

The phase transformation from fcc to L1(0) in FePt nanoparticles was investigated in both thick film samples and self-assembled arrays as a function of the annealing temperature, using transmission electron microscopy, x-ray diffraction, differential scanning calorimetry, and magnetometry. A significant fraction of the surfactant decomposes into gaseous products below 500degreesC, removing the steric barrier between particle cores. This causes the particles to coalesce at the same annealing temperatures where the transformation to the high anisotropy phase occurs. (C) 2003 American Institute of Physics.

DOI： 10.1063/1.1544495

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We find three unanticipated features in the magnetic response of dilute systems of highly monodisperse Fe nanoparticles. Above a spin freezing temperature (Tf) the remanent magnetization relaxes smoothly to zero, but below Tf the relaxation halts abruptly at a nonzero value. The distribution of relaxation rates changes at a percolation temperature (Tp), consistent with chainlike structures above Tp and three-dimensional clusters below Tp. The blocking temperature (Tb) varies inversely proportional to particle diameter, opposite to the behavior of the Néel-Brown model for individual domains, but consistent with a type of Casimir-Polder interaction expected between dilute nanometer-scale particles.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMERICAN PHYSICAL SOC  

We find three unanticipated features in the magnetic response of dilute systems of highly monodisperse Fe nanoparticles. Above a spin freezing temperature (T-f) the remanent magnetization relaxes smoothly to zero, but below T-f the relaxation halts abruptly at a nonzero value. The distribution of relaxation rates changes at a percolation temperature (T-p), consistent with chainlike structures above T-p and three-dimensional clusters below T-p. The blocking temperature (T-b) varies inversely proportional to particle diameter, opposite to the behavior of the Neel-Brown model for individual domains, but consistent with a type of Casimir-Polder interaction expected between dilute nanometer-scale particles.

DOI： 10.1103/PhysRevB.66.172403

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Chemically stabilized 7.0 nm Fe and 3.9 nm FePt nanoparticles have been self-assembled into thin arrays, and imaged by transmission electron microscopy. The local packing structures and stacking sequences of the arrays were uniquely identified by a combination of bright-field imaging and projected potential image simulations. Close-packed structures, hexagonal close-packed (hcp) and face-centered cubic (fcc), were observed for 7.0 nm Fe nanoparticles, while a loosely packed body-centered cubic (bcc) structure was detected for 3.9 nm FePt nanoparticles as well as fcc and hcp. The bcc structure formation is driven by the large vibrational entropy of particles and the soft interparticle repulsions originating from competing enthalpic and entropic effects on surfactant molecule conformation. The sole anomaly noted is a preference for forming hcp arrays with odd numbers of layers observed for Fe nanoparticles. This is attributed to the thickness- and layer-diameter-dependent magnetic coupling between superferromagnetically ordered array layers.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMERICAN PHYSICAL SOC  

Chemically stabilized 7.0 nm Fe and 3.9 nm FePt nanoparticles have been self-assembled into thin arrays, and imaged by transmission electron microscopy. The local packing structures and stacking sequences of the arrays were uniquely identified by a combination of bright-field imaging and projected potential image simulations. Close-packed structures, hexagonal close-packed (hcp) and face-centered cubic (fcc), were observed for 7.0 nm Fe nanoparticles, while a loosely packed body-centered cubic (bcc) structure was detected for 3.9 nm FePt nanoparticles as well as fcc and hcp. The bcc structure formation is driven by the large vibrational entropy of particles and the soft interparticle repulsions originating from competing enthalpic and entropic effects on surfactant molecule conformation. The sole anomaly noted is a preference for forming hcp arrays with odd numbers of layers observed for Fe nanoparticles. This is attributed to the thickness- and layer-diameter-dependent magnetic coupling between superferromagnetically ordered array layers.

DOI： 10.1103/PhysRevB.65.224431

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：A V S AMER INST PHYSICS  

The formation of alloy clusters using a plasma-gas-aggregation technique is described for Co-Al and Co-Pt systems. This method employs two separate elemental sputtering sources and a growth chamber. Metallic vapors generated were cooled rapidly in an Ar atmosphere, and grown into alloy clusters. The composition of the clusters was controlled by adjusting the ratio of the applied sputtering power. We found that B2-CoAl clusters of about 12 nm in diameter were formed for a composition range wider than that predicted by the Co-Al phase diagram, and that high-temperature fcc-CoPt clusters were formed in the Co-Pt system. These findings suggest the nonequilibrium nature of the cluster formation. The size distribution of the clusters is highly monodispersive and does not follow commonly observed log-normal distribution. These results were discussed from the viewpoint of simple gas dynamics. We concluded that monomer absorption with discrete residence time is the dominant mechanism for monodispersive alloy cluster formation, and that the contrasting thermodynamical features between the Co-Al and Co-Pt systems are at the cause of the observed difference in average cluster size. (C) 2002 American Vacuum Society.

DOI： 10.1116/1.1470518

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

The magnetic relaxation of highly diluted monodisperse iron-based particles was measured between 10(-5) and 10(4) s, for different temperatures and particle sizes. The decay over a very broad range of times indicated a distribution of energy barriers remained despite the narrow range of sizes. Many features of this decay could be explained using a percolation model of particles with weak dipolar interactions. However, this model did not predict the abrupt change in the decay rate at long times, which was observed for samples of both 8.0 and 5.5 nm particles below a threshold temperature. (C) 2002 American Institute of Physics.

DOI： 10.1063/1.1452194

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：MATERIALS RESEARCH SOCIETY  

The preparation of monodisperse Fe nanoparticles and self-assembly into hcp and fcc or fcc-like arrays is described. Here dipolar interactions dominate for the interparticle spacings studied (1.4-3.4 nm). Comparison of the low temperature magnetic properties of multilayer arrays with those of dilute suspensions of the same particles show increased coercivity and slower magnetic relaxation in the arrays. Mean field calculations of magnetic interaction fields suggest the type of ordered structures formed.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：MATERIALS RESEARCH SOCIETY  

The preparation of monodisperse Fe nanoparticles and self-assembly into hcp and fee or fcc-like arrays is described. Here dipolar interactions dominate for the interparticle spacings studied (1.4-3.4 nm). Comparison of the low temperature magnetic properties of multilayer arrays with those of dilute suspensions of the same particles show increased coercivity and slower magnetic relaxation in the arrays. Mean field calculations of magnetic interaction fields suggest the type of ordered structures formed.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Funtai Funamtsu Yakin Kyokai/Japan Soc. of Powder Metallurgy  

Cluster-assembling is superior in nano-scale-structure control, where we have to make clusters regular in size to draw out the size-dependent characteristics. Using a plasma-gas-condensation type cluster deposition apparatus, we have succeeded in preparing monodispersed transition metal clusters with the mean sizes d = 5 to 15 nm. We carried out measurement of a transmission electron microscopy and electrical resistivity for clusters randomly deposited on a substrate. The cluster assembling process is interpreted in terms of the percolation theory. The critical percolation thickness, tc, increases with increasing d, while the critical coverage rate estimated from tc is 0.63, being independent of d. tc also increases with increasing the substrate temperature owing to the surface migration of clusters on the substrate. The electrical resistivity and transmission electron microscope image demonstrate the cluster-cluster coalescence above 500 K.

DOI： 10.2497/jjspm.49.615

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The magnetic properties of multilayer arrays of Fe nanoparticles were compared with those of frozen, dilute suspensions of the same particles. The array sample displayed larger coercivity in both hysteretic and remanent magnetization measurements. However, the derivative of the remanent magnetization curve shows a much broader switching field distribution for the arrays than for the dilute sample. Magnetic relaxation measurements show the convergence of the time dependent properties of the samples at large times, and much more rapid relaxation in the arrays at short times.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

CoxAl1-x alloy clusters were synthesized from a mixture of Co and Al metal vapors generated by the sputtering of pure metal targets. We observed that the produced alloy clusters were uniform in size, ranging from approximately 20 nm for Al-rich clusters to 10 nm for Co-rich clusters. For a wide average composition range (x approximate to0.4-0.7), the alloy clusters have the ordered B2 (CsCl-type) structure. In the Co-rich cluster aggregates (x=0.76), the clusters are composed of face-centered-cubic (fcc) Co and minor CoAl(B2) clusters. In the Al-rich aggregates (x=0.23), the clusters are mainly composed of the fcc-Al phase, although clusters occasionally possess a "core-shell structure" with the CoAl(B2) phase surrounded by an Al-rich amorphous phase. These observations are in general agreement with our prediction based on the equilibrium phase diagram. We also noticed that the average composition depends not only on the relative amount of Co and Al vapors, but also on their absolute amount, and even on the Ar gas flow rate, which promotes mixing and cooling the two vapors. These findings show that the formation of alloy clusters in vapor phase is strongly influenced by the kinetics of cluster formation, and is a competing process between the approach to equilibrium and the quenching of the whole system. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1394918

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Arrays were self-assembled by evaporating suspensions of 4 nm FePt or 8 nm Fe nanoparticles. The monolayers had a hexagonal close packed (hcp) structure, but the multilayer structure varied. To identify the multilayer structures, transmission electron microscopy (TEM) images were compared with phase contrast image simulations. The results showed that Fe could be grown as both hcp and face-centered cubic (fcc), or fcc-like, structures. The results of image analysis of the FePt arrays were consistent with fcc structures.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：INST PURE APPLIED PHYSICS  

We demonstrate that composition of alloy clusters can easily be controlled by plasma gas aggregation technique, where two separate sources were placed face-to-face within a same sputtering chamber. Size of the alloy clusters prepared in this study is monodispersive, in the range of 5 to 20 nm in average diameters. Our structural study suggested that the cluster forming process is dictated by the competition between the approach to equilibrium and rapid quenching in the vapor phase.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：INST PURE APPLIED PHYSICS  

This article first describes a plasma-gas-condensation cluster deposition system and forming ability of monodtspersed size clusters. Then, it deals with the characteristic properties of Co clusters and Co/CoO core-shell cluster assemblies. In monodispersed size Co clusters, superparamagnetic to ferromagnetic transition is detected at around 8 nm in diameter at room temperature. Co/CoO coreshell cluster assemblies reveal a Coulomb blockade effect in the tunneling conductivity and magnetoresistance, and a macroscopic quantum tunneling effect in the magnetic relaxation at low temperatures, being well distinguished from thermal activation type behaviors at high temperatures. These results demonstrate that formation of monodispersed size clusters is a key to control physical properties of cluster assembled materials.

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Monodispersed Co/CoO cluster assemblies with the mean cluster sizes of 6 and 13 nm have been prepared by a plasma-gas condensation type cluster beam deposition apparatus. We measured the effects of the oxygen gas flow rate during deposition, temperature, and cluster size on the coercivity and hysteresis loop shift induced by field cooling. The large exchange bias field (10.2 kOe) and coercivity (5 kOe) were observed at 5 K for the monodispersed Co/CoO cluster assembly with d=6 nm. The correlations between unidirectional anisotropy and uniaxial anisotropy, training effect and magnetic relaxation can be interpreted by the hypothesis of a spin disorder in the interfacial layer between the antiferromagnetic CoO shell and the ferromagnetic Co core. ©2000 The American Physical Society.

DOI： 10.1103/PhysRevB.61.3103

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP PUBLISHING LTD  

X-ray absorption near edge structure (XANES) spectra and x-ray magnetic circular dichroism (XMCD) spectra at the Co K edge have been measured for Co clusters with the mean diameter d = 6-13 nm. The spectral analysis indicates that the fee phase is predominant for d = 6 nm, while the hcp phase gradually increases with increasing d in agreement with the results of transmission electron microscopy. The 4p orbital moments of clusters tend to decrease in the smaller cluster, but the reduction is small compared with the case of the multilayers, suggesting the importance of surface effects of the Co cluster system.

DOI： 10.1088/0953-8984/12/14/320

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER PHYSICAL SOC  

Monodispersed Co/CoO cluster assemblies with the mean cluster sizes of 6 and 13 nm have been prepared by a plasma-gas condensation type cluster beam deposition apparatus. We measured the effects of the oxygen gas flow rate during deposition, temperature, and cluster size on the coercivity and hysteresis loop shift induced by field cooling. The large exchange bias field (10.2 kOe) and coercivity (5 kOe) were observed at 5 K for the monodispersed Co/CoO cluster assembly with d=6 nm. The correlations between unidirectional anisotropy and uniaxial anisotropy, training effect and magnetic relaxation can be interpreted by the hypothesis of a spin disorder in the interfacial layer between the antiferromagnetic CoO shell and the ferromagnetic Co core.

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We have fabricated CoO-coated monodispersive Co cluster assemblies with the mean cluster size of 13 nm at various oxygen gas-flow rate RO2 by a plasma-gas-condensation-type cluster beam deposition technique, and studied their electrical conductivity, σ, and magnetoresistance. For RO2<0.24 SCCM (sccm denotes cubic centimeter per minute), the resistivity revealed a minimum and showed In T dependence at lower temperatures, probably due to the weak localization of conduction electrons owing to presence of thin oxide shells covering Co cores. A small negative magnetoresistance was observed in this regime. For RO2>0.3 SCCM, tunnel-type temperature dependence of σ in the form of ln σ vs 1/T was observed between 7 and 80 K. This differs from the well-known temperature dependence of ln σ vs 1/T1/2 for disordered granular materials. The magnetoresistance ratio, (ρH=30 kOe-ρ0)/ρ0, is negative and its absolute value increases sharply with decreasing temperature below 25 K: from 3.5% at 25 K to 20.5% at 4.2 K. This marked increase, by a factor of 6, is much larger than those observed for conventional metal-insulator granular systems. These results are ascribed to a prominent cotunneling effect in the Coulomb blockade regime, arising from the uniform Co core size and CoO shell thickness in the present monodispersed cluster assemblies. ©1999 The American Physical Society.

DOI： 10.1103/PhysRevB.60.2093

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN INST METALS  

We have studied the structure and magnetic properties of monodispersed Co cluster assemblies with mean diameter, d = 6-13 nm. In these Co cluster assemblies, an fee phase is predominant, whereas the volume fraction of an hcp phase increases with increasing d from 6 to 13 nm. At a thin deposition stage (average thickness, t = 1 nm), Co clusters are nearly isolated. At 300 K, they are superparamagnetic for d = 6 nm, while ferromagnetic for d = 8.5 and 13 nm. With increasing t, the superparamagnetic to ferromagnetic transition is detected for d = 6 nm. For d = 6-13 nm, the magnetic coercivity, H-c, rapidly increases at t = 2-4 nm, near or below the geometrical and electrical percolation thresholds. However, H-c is almost independent of t up to t = 100 nm.

DOI： 10.2320/matertrans1989.40.1450

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

Magnetic properties have been measured for monodisperse-sized Co/CoO cluster assemblies prepared by a plasma-gas-condensation-type cluster beam deposition technique. The clear correlation obtained between exchange bias field and coercivity suggests the enhancement of uniaxial anisotropy owing to the exchange coupling between the ferromagnetic Co core and antiferromagnetic CoO shell, and magnetic disorder at the core-shell interface. A nonthermal magnetic relaxation observed below 8 K, being referred to as macroscopic quantum tunneling of the magnetization, is ascribed to the enhanced uniaxial anisotropy. (C) 1999 American Institute of Physics. [S0003-6951(99)02150-6].

DOI： 10.1063/1.125479

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER VERLAG  

Nanometer-sixed Cr clusters in the size rage of 8.5-13 nm have been produced by a plasma gas condensation-type cluster deposition apparatus, which combines a glow-discharge sputtering technique with an inert gas condensation technique. We have studied the effects of sputter power, Ar gas pressure, P-Ar, and Ar gas flow rate, V-Ar, on the size distribution of Cr clusters by transmission electron microscopy. The cluster size is insensitive to the sputter power, while the nucleation process is promoted when the sputter power is increased. Monodispersive Cr clusters are formed at both low P-Ar and low V-Ar, where the nucleation and growth processes are definitely separated, and the coagulation of growing particles is prohibited. In the present experiments, these conditions are effectively attained by the use of a carrier gas flow and liquid nitrogen cooling of the cluster growth region.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER INST PHYSICS  

Co-cluster-assembled films have been prepared using a size-controllable cluster beam deposition system, by which monodispersed Co clusters with a mean diameter, d=6-13 nm are available. Their morphology and magnetic properties have been studied by scanning electron microscopy (SEM), small-angle x-ray scattering (SAXS) and magnetization measurements. The SEM images show that the film has a porous structure consisting of fine grains without a columnar texture and its density is about 25% of the bulk Co. The SAXS measurements indicate that monodispersivity of the incident clusters is maintained through their assembling process only for d=13 nm. All the specimens exhibit ferromagnetic behavior at room temperature and the magnetic coercive field H-c rapidly increases with decreasing temperature: H-c=168 kA/m (2.1 kOe) at 5 K. Such an enhancement in H-c is ascribed to the exchange anisotropy which arises from the antiferromagnetic Co-oxide layers covering the Co clusters, and to the assemblies of single-domain ferromagnetic clusters with the structure modification and magnetic interaction among them. The monotonic increase in H-c at 300 K with increasing d is simply understood in terms of the single-domain particle theory. (C) 1999 American Institute of Physics. [S0021-8979(99)04722-2].

DOI： 10.1063/1.371585

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/jinstmet1952.63.9_1117

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER PHYSICAL SOC  

We have fabricated CoO-coated monodispersive Co cluster assemblies with the mean cluster size of 13 nm at various oxygen gas-flow rate R-O2 by a plasma-gas-condensation-type cluster beam deposition technique, and studied their electrical conductivity, sigma, and magnetoresistance. For R-O2<0.24 SCCM (sccm denotes cubic centimeter per minute), the resistivity revealed a minimum and showed In T dependence at lower temperatures, probably due to the weak localization of conduction electrons owing to presence of thin oxide shells covering Co cores. A small negative magnetoresistance was observed in this regime. For R-O2>0.3 SCCM, tunnel-type temperature dependence of sigma in the form of In sigma vs 1/T was observed between 7 and 80 K. This differs from the well-known temperature dependence of In sigma vs 1/T-1/2 for disordered granular materials. The magnetoresistance ratio, (rho(H=30) (kOe)- rho(0))/rho(0), is negative and its absolute value increases sharply with decreasing temperature below 25 K: from 3.5% at 25 K to 20.5% at 4.2 K. This marked increase, by a factor of 6 is much larger than those observed for conventional metal-insulator granular systems. These results are ascribed to a prominent cotunneling effect in the Coulomb blockade regime, arising from the uniform Co core size and CoO shell thickness in the present monodispersed cluster assemblies. [S0163-1829(99)06527-3].

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP PUBLISHING LTD  

We deposited monodispersed Go-clusters in the size range of 6-13 nm on substrates using the plasma-gas-condensation cluster deposition system. The assembling process of the clusters from discontinuous to continuous networks was investigated by transmission electron microscopy (TEM) and in situ electrical conductivity measurement, and discussed in terms of the two-dimensional (2D) percolation concept. The electrical conductivity measurement indicates that the percolation process of Co clusters does not agree with a simple scaling-law: the critical conductivity exponent increases with increasing mean cluster diameter, d, although it is predicted to be independent of d in the ordinary 2D percolation theory. This anomaly is interpreted by the soft-percolation model, implying that there is distribution of electrical contacts between the clusters. The critical coverage of clusters (0.63) is much higher than the predicted one (0.45) irrespective of d, due mainly to the partial overlapping of deposited clusters, and partly to an attractive interaction between the clusters. Such cluster-overlapping also increases the critical thickness of electrical percolation with increasing d.

DOI： 10.1088/0953-8984/11/16/006

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-V C H VERLAG GMBH  

Oxide-coated monodispersive Co duster assemblies with the mean cluster size of 6 and 13 nm have been prepared by a plasma-gas-condensation type cluster beam deposition apparatus. The magnetic properties of the samples prepared without and with introducing oxygen gas into the deposition chamber are compared. The exchange anisotropy induced by interfacial exchange coupling between the ferromagnetic Co core and the antiferromagnetic cobalt oxide shell has been studied by measuring the hysteresis loop shift of the field-cooled samples and the low field thermomagnetic curve.

DOI： 10.1002/(SICI)1521-396X(199903)172:1<209::AID-PSSA209>3.0.CO;2-V

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記述言語：英語   出版者・発行元：PHYSICAL SOC JAPAN  

We studied the two-dimensional assembling process of nanometer-size Co clusters on substrates in terms of the percolation theory. We demonstrate the nonuniversal behavior of the electrical conductivity depending strongly on the cluster size, d: the conductivity critical exponent increases from 1.1 to 1.8 with increasing d from 6 to 13 nm. The soft-percolation model, which takes into account the wide distribution of connectivity between clusters, is a candidate to explain this nonuniversality.

DOI： 10.1143/JPSJ.68.28

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Nanometer-sized Cr clusters in the size range of 7.6-13 nm have been produced by a plasma-gas-condensation-type cluster deposition apparatus, which combines a grow-discharge sputtering technique with an inert gas condensation technique. We have studied influences of the Ar gas pressure, PAr, and the Ar gas flow rate, VAr, on the size distribution of Cr clusters by transmission electron microscopy. Monodispersed Cr clusters are formed at both low PAr and low VAr. At low PAr, Cr clusters nucleate and grow only in the liquid-nitrogen-cooled growth region, and the deposition rate is rather low. At high PAr, on the other hand, a large amount of Cr clusters are formed even near the sputtering source, and the nucleation and growth occur over a wide region between the sputtering source and the growth region. Under this condition, the deposition rate is relatively high. Consequently, the formation mechanism of the monodispersed clusters is similar to that of monodispersed colloidal particles: The nucleation and growth processes are definitely separated and the coagulation of growing particles is prohibited. In the present experiments, these conditions are effectively attained by using a carrier gas flow and liquid-nitrogen-cooling of the cluster growth region. © 1999 American Institute of Physics.

DOI： 10.1063/1.369476

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Inst of Metals  

We have deposited monodispersed Co clusters on substrates using a plasma-gas-condensation-type cluster deposition system. We have studied their two-dimensional assembling process by transmission electron microscopy, in situ electrical conductivity and magnetization measurements in terms of the percolation theory. The electrical conductivity measurement indicates that the critical thickness and conductivity critical exponent depend strongly on the cluster size. The soft-percolation model, which takes into account the wide distribution of connectivity between clusters, is a candidate model to explain this nonuniversality. The critical coverage of clusters (0.63) is much higher than the predicted one (0.45) irrespective of d, due mainly to the partial overlapping of deposited clusters, and partly to an attractive interaction between clusters. The magnetic properties evolve at around and/or below geometrical and electrical percolation thresholds for all the samples.

DOI： 10.2320/jinstmet1952.63.9_1117

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

We have studied electrical conductivity, σ, and magnetoresistance in a CoO-coated monodispersive Co cluster assembly fabricated by a plasma-gas-aggregation-type cluster beam deposition technique. The temperature dependence of σ is described in the form of log σ vs 1/T for 7&lt
T&lt
80 K. The magnetoresistance ratio (ρ 0-ρ 3T)/ρ 0 increases sharply with decreasing temperature below 25 K: from 3.5% at 25 K to 20.5% at 4.2 K. This marked increase (by a factor of 6) is much larger than those observed for conventional metal-insulator granular systems. These results are ascribed to the Coulomb blockade effect in the monodispersed cluster assemblies. © 1999 American Institute of Physics.

DOI： 10.1063/1.122956

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCI LTD  

Transmission electron microscopy observation was carried out for nanometric Cr clusters deposited on microgrids at room temperature using plasma-gas-condensation (PGC) method. In order to obtain optimum conditions for monodisperse cluster formation we have studied effects of an Ar gas pressure, an Ar gas flow rate, and a mixing rate of He gas with Ar gas on the size distribution of formed clusters. It has been found that monodisperse clusters with the size rage of 9-13 nm in diameter are producible at a low Ar gas pressure (less than or equal to 1.3 Torr) and a low Ar gas flow rate (less than or equal to 600 seem). The mean cluster size decreases with decreasing Ar gas pressure, while it is not sensitive to the Ar gas flow rate. When He gas is mixed with Ar gas, the mean cluster size further decreases to 6 nm and the cluster beam intensity becomes stronger probably because He gas with the high thermal conductivity enhances supersaturation for cluster nucleation. (C) 1998 Elsevier Science Limited. All rights reserved.

DOI： 10.1016/S0968-5677(98)00014-5

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：AMER INST PHYSICS  

Nanometric Cr clusters have been prepared by Plasma-Gas-Aggregation, which is a combination of sputtering and gas-aggregation techniques. We studied influences of the flow rate and sorts of inert gas(Ar and He/Ar mixture) on formed clusters by transmission electron microscope(TEM) observations. The mean cluster diameter as a function of the Ar gas flow rate shows the anomalous behavior in comparison with the conventional gas-aggregation method: the mean cluster diameter has a maximum value at the Ar gas flow rate=600 SCCM, indicating that there is an optimum Ar gas flow rate for cluster formation. This behavior can be attributed to the balance of sputtering rate and thermalization process of sputtered atoms. It is also found that the low flow rate of Ar gas leads to mono-disperse nanometric clusters in the size range of about 5-10 nm. The cluster size further decreases when He gas is mixed with Ar gas.

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記述言語：日本語  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Si-C-Ti-O fibers pyrolyzed from polytitanocarbosilane polymer precursors have been observed by a high-resolution transmission electron microscope. Nano-crystalline clusters are finely dispersed in the amorphous matrices of Si-C-Ti-O fibers made from thermal-oxidation-cured and electron-irradiation-cured precursors. Nano-beam electron diffraction and simulated patterns demonstrate that these clusters are β-SiC. Such cluster formation is enhanced in the specimens heat-treated at a high temperature and cured by electron-irradiation.

DOI： 10.2320/matertrans1989.38.5

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE  

The formation and thermal stability of nanocrystalline Cu70Ti20Ni10 powders by mechanical alloying has been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). After milling, the material has a disordered fee structure, with nanocrystalline grain sizes around 4.7 nm determined from the fee (111) diffraction peak. The DSC signal monotonically decreases with isothermal transformation owing to grain growth. The crystal grains do not grow by heating until the intermetallic TiCu3 and NiTi phases nucleate at 450 degrees C.

DOI： 10.1016/S0921-5093(96)10347-6

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE  

Fe/Cu and Fe/Ag granular alloy films have been produced using a cluster-beam source: Fe clusters from the nozzle of a high temperature crucible are directly dispersed in Cu and Ag matrices obtained by simultaneous vapor deposition. They reveal a giant magnetoresistance effect without any heat treatment. High-resolution transmission electron microscope observations indicate the presence of nanometric Fe clusters together with ten-nanometer sized geometrical an chemical fluctuations in these films. Extended X-ray absorption fine structure experiments indicate that the local structure around Fe atoms is fcc for Fe concentrations less than 22 at.% and bcc for more than 35 at.% Fe in Cu matrices, while the structure of the Fe cluster is distorted bcc-like even for low Fe content down to 12 at.% in Ag matrices. These results suggest that small Fe clusters can diffuse on the substrate to form larger clusters. Small Fe clusters also intermix with Cu and Ag matrices to give rise to nanoscale heterogeneity. However, since the immiscibility of Fe with Ag is more remarkable than that with Cu, aggregation of Fe clusters is accelerated in Ag matrices.

DOI： 10.1016/S0921-5093(96)10335-X

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE  

Fe-Ag granular materials, which comprise iron clusters in a silver matrix, have been prepared by a cluster beam method, and their local structures have been investigated with high resolution transmission electron microscopy (HRTEM) and magnetogranulometry. They show that the silver matrix grows into columnar grains of 20-30 nm in diameter, in which iron clusters of about 5 nm in diameter are dispersed. The density of iron clusters increases with increasing the iron content of the films although the size of iron clusters changes little. The results of magnetogranulometry are consistent with those of TEM observations. These results enable us to account for compositional dependence of magnetoresistance: the iron clusters magnetically contact each other to attain percolation at 20-30 at.% Fe, giving rise to the maximum MR ratio.

DOI： 10.1016/S0921-5093(96)10338-5

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Fe clusters have been dispersed in Ag matrices using cluster beam (CB) sources without any heat treatment. Their structure and morphology have been studied by comparison with those of the sputter-deposited Fe-Ag alloys using small angle X-ray scattering, high resolution transmission electron microscopy and extended X-ray absorption fine structure measurements. In the granular alloys made by CB, bcc Fe clusters of a few nanometers dimension are detected, together with ten-nanometer scale geometrical and chemical fluctuations. In the sputter-deposited alloys, the Fe atoms are rather well mixed with the Ag atoms in the as-deposited state, and fee Fe clusters are first formed and transform to larger bce particles with increasing annealing temperature. The field-dependence of the magnetoresistance is well correlated with the growth mode of the Fe clusters in the granular alloys.

DOI： 10.1016/0022-3093(95)00403-3

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Using cluster beam sources, we have obtained FeAg granular films, which display giant magnetoresistance, GMR, without any heat treatment. The experimental results of small angle X-ray scattering and high-resolution transmission electron microscopy indicate that a few nanometer Fe clusters are embeded in Ag matrices with 10 nm order geometrical and chemical fluctuations. The extended X-ray absorption fine structure measurement indicates that the short range structure of Fe clusters is bcc but distorted in the as-deposited state. The magnetoresistance (MR) does not saturate at 140 kOe: conduction-electrons suffer spin-disorder scattering even in high fields, because small Fe clusters in Ag matrices reveal a spin-glass character and Fe atoms at the interface a superparamagnetic. After annealing above 570 K, MR saturates at high fields, which is ascribed to the ferromagnetism of grown Fe clusters. The concentration dependence of electrical resistivity and MR can be interpreted by geometrical and magnetic percolation of nanometric Fe clusters. © 1995.

DOI： 10.1016/0921-5107(94)08027-5

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Fe Ag granular films prepared by ion cluster beam exhibit the largest magnetoresistance (MR) in the as-deposited state, while those prepared by sputtering show the maximum MR after being annealed at 573 K. The high-resolution electron micrographs indicate that the nanometric Fe clusters in Ag matrices are crucial for the large MR. © 1995.

DOI： 10.1016/0304-8853(94)00735-7

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Crystallites of scandium carbides nesting in multilayered, polyhedral graphitic cages (nanocapsules) were produced by evaporating a scandium-graphite composite rod by electric arc discharge in helium gas. The composite particles were characterized by analytical electron microscopy and X-ray diffraction. The encapsulated scandium carbide was identified to be SC15C19, instead of dicarbide RC2 (R represents rare-earth elements) which was the form of carbide commonly found for other rare-earth elements entrapped in nanocapsules. The size of the capsules ranged from about 10 to 100 nm. Morphological features of the outer graphitic carbon, multilayered and polyhedral, were quite similar to those previously discovered for the capsules protecting RC2 (R=Y, La, Ce, ··· ,Lu). © 1994 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.33.L186

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Fine particles of cobalt and cobalt carbide nesting in multilayered graphitic sheets, which were synthesized by an electric arc discharge of carbon rods containing cobalt oxide (CoO), were studied by transmission electron microscopy, including microdiffraction and energy dispersive x-ray analysis. The size of the wrapped particles was typically in a range from 50 to 200 nm. Three phases of nested materials, hcp(α)-Co, fcc(β)-Co, and Co 3C, were identified.

DOI： 10.1063/1.355901

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Fine particles of iron and iron carbide wrapped in multilayered graphitic sheets, which were synthesized by arc discharge of carbon rods containing iron oxide (Fe2O3), were studied by transmission electron microscopy. The size of the wrapped particles was typically in the range 20-200 nm. Two kinds of nested materials were found; one was alpha-Fe and the other, Fe3C (cementite).

DOI： 10.1016/0009-2614(93)89341-E

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN INST METALS  

Ag metal clusters have been formed on carbon films supported by collodion-coated microgrids with ion-cluster-beam method and observed with a transmission electron microscope. The average size, d, of Ag clusters is about 2 nm and its dispersion, DELTAd, 1 nm for the deposition time, t=15 s, being independent of the deposition conditions. d=12 nm and DELTAd=3 nm for t=30 s, while d=12 nm and DELTAd=7 nm for t=60 s on room temperature substrates. d is larger on a room temperature than on a liquid-nitrogen-cooled substrate and it decreases by ionization and acceleration of the incident beam. The crystallinity is better on room temperature substrates than on liquid-nitrogen-cooled substrates.

DOI： 10.2320/matertrans1989.34.646

Web of Science

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記述言語：日本語  

J-GLOBAL

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記述言語：日本語   出版者・発行元：日本化学会  

CiNii Books

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記述言語：日本語   出版者・発行元：The Japanese Society of Microscopy  

DOI： 10.11410/kenbikyo1950.38.219

CiNii Books

J-GLOBAL

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

CiNii Books

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

CiNii Books

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

CiNii Books

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記述言語：日本語  

CiNii Books

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記述言語：日本語  

CiNii Books

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記述言語：日本語  

CiNii Books

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記述言語：日本語  

J-GLOBAL

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

CiNii Books

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

CiNii Books

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記述言語：英語   出版者・発行元：WILEY-V C H VERLAG GMBH  

Oxide-coated monodispersive Co duster assemblies with the mean cluster size of 6 and 13 nm have been prepared by a plasma-gas-condensation type cluster beam deposition apparatus. The magnetic properties of the samples prepared without and with introducing oxygen gas into the deposition chamber are compared. The exchange anisotropy induced by interfacial exchange coupling between the ferromagnetic Co core and the antiferromagnetic cobalt oxide shell has been studied by measuring the hysteresis loop shift of the field-cooled samples and the low field thermomagnetic curve.

DOI： 10.1002/(SICI)1521-396X(199903)172:1<209::AID-PSSA209>3.0.CO;2-V

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

CiNii Books

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記述言語：日本語   出版者・発行元：一般社団法人日本物理学会  

CiNii Books

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記述言語：日本語   掲載種別：記事・総説・解説・論説等（大学・研究所紀要）  

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記述言語：日本語   出版者・発行元：アグネ技術センター  

CiNii Books

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記述言語：日本語  

CiNii Books

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記述言語：日本語  

J-GLOBAL

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記述言語：英語  

Crystallites of scandium carbides nesting in multilayered, polyhedral graphitic cages (nanocapsules) were produced by evaporating a scandium-graphite composite rod by electric arc discharge in helium gas. The composite particles were characterized by analytical electron microscopy and X-ray diffraction. The encapsulated scandium carbide was identified to be SC15C19, instead of dicarbide RC2 (R represents rare-earth elements) which was the form of carbide commonly found for other rare-earth elements entrapped in nanocapsules. The size of the capsules ranged from about 10 to 100 nm. Morphological features of the outer graphitic carbon, multilayered and polyhedral, were quite similar to those previously discovered for the capsules protecting RC2 (R=Y, La, Ce, ··· ,Lu). © 1994 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.33.L186

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開催年月日： 2024年6月

記述言語：日本語   会議種別：口頭発表（一般）  

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開催年月日： 2019年6月

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開催年月日： 2019年6月

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開催年月日： 2019年5月

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The preparation of monodisperse Fe nanoparticles and self-assembly into hcp and fcc or fcc-like arrays is described. Here dipolar interactions dominate for the interparticle spacings studied (1.4-3.4 nm). Comparison of the low temperature magnetic properties of multilayer arrays with those of dilute suspensions of the same particles show increased coercivity and slower magnetic relaxation in the arrays. Mean field calculations of magnetic interaction field suggest the type of ordered structures formed.

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Cluster-assembling is superior in nano-scale-structure control, where we have to make clusters regular in size to draw out the size-dependent characteristics. Using a plasma-gas-condensation type cluster deposition apparatus, we have succeeded in preparing monodispersed transition metal clusters with the mean sizes d = 5 to 15 nm. We carried out measurement of a transmission electron microscopy and electrical resistivity for clusters randomly deposited on a substrate. The cluster assembling process is interpreted in terms of the percolation theory. The critical percolation thickness, tc, increases with increasing d, while the critical coverage rate estimated from tc is 0.63, being independent of d. tc also increases with increasing the substrate temperature owing to the surface migration of clusters on the substrate. The electrical resistivity and transmission electron microscope image demonstrate the cluster-cluster coalescence above 500 K.

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記述言語：日本語  

Cluster-assembling is superior in nano-scale-structure control, where we have to make clusters regular in size to draw out the size-dependent characteristics. Using a plasma-gas-condensation type cluster deposition apparatus, we have succeeded in preparing monodispersed transition metal clusters with the mean sizes d=5 to 15nm. We carried out measurement of a transmission electron microscopy and electrical resistivity for clusters randomly deposited on a substrate. The cluster assembling process is interpreted in terms of the percolation theory. The critical percolation thickness, t<SUB>c</SUB>, increases with increasing d, while the critical coverage rate estimated from t<SUB>c</SUB> is 0.63, being independent of d. t<SUB>c</SUB> also increases with increasing the substrate temperature owing to the surface migration of clusters on the substrate. The electrical resistivity and transmission electron microscope image demonstrate the cluster-cluster coalescence above 500K.

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記述言語：日本語   会議種別：シンポジウム・ワークショップ パネル（指名）  

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記述言語：日本語   会議種別：ポスター発表  

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