Influence of size distribution on the magnetocaloric effect of superparamagnetic gold–magnetite nanocomposite
| Autor: | Kenji Okitsu, Takao A. Yamamoto, Tadachika Nakayama, Takuya Kinoshita, K. Niihara, Satoshi Seino, Takashi Nakagawa, Yohei Otome, H. Maruyama |
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| Rok vydání: | 2004 |
| Předmět: |
Magnetic measurements
Materials science Nanocomposite Condensed matter physics Mechanical Engineering Metals and Alloys Mineralogy chemistry.chemical_compound Magnetization Transition metal chemistry Mechanics of Materials Transmission electron microscopy Materials Chemistry Magnetic refrigeration Magnetite Superparamagnetism |
| Zdroj: | Journal of Alloys and Compounds. 365:281-285 |
| ISSN: | 0925-8388 |
| DOI: | 10.1016/s0925-8388(03)00663-7 |
| Popis: | The magnetocaloric effect of the superparamagnetic nanocomposite composed of magnetite grains isolated by gold was investigated as a function of the size distribution width. The magnetic entropy change ΔS was evaluated by applying Maxwell’s relation to the magnetization data sets measured at various temperature and applied field. The size distribution was evaluated by the TEM observation, showing that the average sizes were from 4.6 to 7.4 nm and the geometric standard deviations σg from 1.32 to 1.59. Thus evaluated ΔS was found to increase with decreasing σg, demonstrating our previous anticipation that the narrow size distribution would much enhance the magnetocaloric effect of the superparamagnetic nanocomposite material. The ΔS was several times larger than that of our previous nanocomposite composed of γ-Fe2O3 and silver. |
| Databáze: | OpenAIRE |
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