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Magnetic Entropy Change of Nanocomposites Composed of a Silver Matrix and Grains of Iron-Oxide Or -Nitride

Published online by Cambridge University Press:  21 February 2011

T. A. Yamamoto ,
M. Tanaka ,
K. Shiomi ,
T. Nakayama ,
K. Nishimaki ,
T. Nakagawa ,
T. Numazawa ,
M. Katsura  and
K. Niihara
T. A. Yamamoto
Affiliation:
Department of Nuclear Engineering, Osaka University, 2-1 Yamadaoka, Suita, saka 565-0871, Japan. takao@nucl.eng.osaka-u.ac.jp
M. Tanaka
Affiliation:
Department of Nuclear Engineering, Osaka University, 2-1 Yamadaoka, Suita, saka 565-0871, Japan. takao@nucl.eng.osaka-u.ac.jp
K. Shiomi
Affiliation:
Department of Nuclear Engineering, Osaka University, 2-1 Yamadaoka, Suita, saka 565-0871, Japan. takao@nucl.eng.osaka-u.ac.jp
T. Nakayama
Affiliation:
Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, saka 567-0047, Japan
K. Nishimaki
Affiliation:
Department of Nuclear Engineering, Osaka University, 2-1 Yamadaoka, Suita, saka 565-0871, Japan. takao@nucl.eng.osaka-u.ac.jp
T. Nakagawa
Affiliation:
Department of Nuclear Engineering, Osaka University, 2-1 Yamadaoka, Suita, saka 565-0871, Japan. takao@nucl.eng.osaka-u.ac.jp
T. Numazawa
Affiliation:
Magnet Laboratories, National Research Institute for Metals, 1-2-1, Sengen, sukuba 305-0003, Japan
M. Katsura
Affiliation:
Department of Nuclear Engineering, Osaka University, 2-1 Yamadaoka, Suita, saka 565-0871, Japan. takao@nucl.eng.osaka-u.ac.jp
K. Niihara
Affiliation:
Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, saka 567-0047, Japan
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Abstract

Magnetocaloric effect of nanocomposites composed of iron-oxide or iron-nitride grains dispersed in a silver matrix was studied by calculating magnetic entropy change ΔS induced by a change in applied magnetic field H. These nanocomposites were synthesized by the inert gas condensation technique and nitridation by heat treatment in an ammonia gas stream. Average sizes of the iron-containing grains were 10-35 nm. Magnetic phases in the materials were Fe3O4 or γ -Fe2O3 for the oxide-composites and γ-Fe4N or ε -Fe3N for the nitride-composites. Values of the ΔS were obtained by applying a thermodynamic Maxwell's relation, (∂S / ∂H)T = (∂M / ∂T)H, to data set of magnetization M measured at various temperatures T. They clearly indicated significant enhancement due to the nanostructure as predicted.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 581: Symposium F – Nanophase & Nanocomposite Materials II , 1999 , 297
Copyright
Copyright © Materials Research Society 2000

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References

REFERENCES

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