著者

齋藤 明子 加治 志織 小林 忠彦 中込 秀樹

出版者

公益社団法人 低温工学・超電導学会 (旧 社団法人 低温工学協会)

雑誌

低温工学 (ISSN:03892441)

巻号頁・発行日

vol.50, no.2, pp.88-95, 2015-02-25 (Released:2015-04-06)

参考文献数

40

被引用文献数

1

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The development of magnetic refrigerants and basic research on active magnetic regenerative (AMR) refrigeration at room temperature were performed. Temperature differences between the hot and cold ends of the AMR unit of more than 45 degrees, and achieving the lowest temperature of minus 10 degrees were obtained by operating the AMR cycle with a NdFeB Halbach-type permanent magnet and spherical-shaped GdY magnetic refrigerants. In the case of the La(Fe,Co,Si)13 compound, the temperature difference between the ends of the AMR unit reached only 21 degrees. This is mainly attributed to the fact that larger specific heat provides smaller temperature changes in the magnetocaloric effect even if the La(Fe,Co,Si)13 compound shows larger magnetic entropy change than Gd alloys. At the same time, large specific heat is effective for load characteristics. Model calculations indicated that multi-layered magnetic refrigerants whose magnetic transition temperatures are tailored to the temperature gradient in the AMR unit improve both temperature difference and load characteristics. Ideal design for achieving optimized heat flow and regeneration leads to the room-temperature application.

著者

加治 志織 大橋 政司 三谷 誠司 高梨 弘毅 巨海 玄道

出版者

九州大学理学部極低温実験室

雑誌

九州大学極低温実験室だより (ISSN:13460161)

巻号頁・発行日

vol.4, pp.19-24, 2003-06

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Co-Al-0グラニュラー薄膜は、Co粒子がAl酸化物絶縁相にナノスケールで分散した構造をもつ金属-非金属グラニュラー物質でトンネル型磁気抵抗効果(Tunnel Magnetoresistance:TMR)を示す典型的物質である。今回我々は低温・高圧下でこの物質の電気抵抗の測定を行い、その特徴ある温度依存性の圧力変化及びTMRの加圧による増大を測定した。これらの結果について概観し、その背後に横たわる物理的な機構を考察する。Co-Al-O granuler films consist of nanometer-sized Co granules embedded in an Al-oxide matrix, which are typical examples exhibiting tunnel magnetroresistance(TMR). We have measured the electrical resistance of this granular film under high pressure and magnetic field. It is found that the temperature dependence of resistivity is affected strongly and TMR is enhanced by applying pressure. We suggested that the higher order tunneling model is able to explain the experimental results.