Magnetic refrigerant Magnetic character change in compounds La(Fe 1-x Co x ) 11.2 Si 1.8 Soichiro Sasaki Suzuki Kusakabe lab.

Contents 1 Introduction 2 magnetic character of compounds La(Fe 1-x Co x ) 11.2 Si Summary

1-1 problem of refrigerant technology uses gas Not clean energy 環境にやさしくない Using CFC (chlorofluorocarbon) or a CFC substitute フロンや代替フロンは地球温暖化の原因 Bad energy efficient work ピストンを使用するため熱効率が悪い Compressor, noise, vibration コンプレッサによる圧縮、膨張、弁操作振動、騒音 Magnetic refrigerant 磁気冷凍

1-2 comparison between gas and magnetic refrigerant Magnetic refrigerant Gas refrigerant generation of heat absorption of heat compressionexpanding Adding a magnetic field Reducing a magnetic field

1-3 magnetic refrigerant cycle (1)Isothermal magnetization 等温磁化 (2)Adiabatic demagnetization 断熱消磁 (3)Absorbing heat 吸熱 （３）（３） (A→B) (B→C) （ H １ ＞ H ２ ）

1-4 the necessary factor of magnetic refrigerant Maxwell equation To get big ΔS ・ High magnetization ・ Soft ferromagnetism ex. Compound of Gd or Dy

The structure of compound La(Fe 1-x- ｙ Co x Si ｙ ) 13 (Co) 1/8 unit sell Top view of 1/8 unit sell Cubic NaZn 13 a-type structure Cluster of Icosahedron (20 面体）

Magnetic character of compounds La(Fe x Si 1-x ) 13 A. Fujita, Y. Akamatsu and K. Fukamichi. J. Appl. Phys. 85 (1999), p La(Fe 0.86 Si 0.14 ) 13 La(Fe 0.88 Si 0.12 ) 13

Character of compounds La(Fe x Si 1-x ) 13 S. Fujieda, A. Fujita, and K. Fukamichi Applied Physics Letters -- August 12, Volume 81, Issue 7, pp. 1

Magnetizatic entropy change and its temperature variation in compounds La(Fe 1-x Co x ) 11.2 Si 1.8 F. X. Hu, X. L. Qian, et al. J. Appl. Phys. 92, 3620 (2002)

Magnetization-Temperature graph F. X. Hu, X. L. Qian, et al. J. Appl. Phys. 92, 3620 (2002) H=0.01T

Magnetization-Magnetic field graph F. X. Hu, X. L. Qian, et al. J. Appl. Phys. 92, 3620 (2002)

Entropy-temperature graph F. X. Hu, X. L. Qian, et al. J. Appl. Phys. 92, 3620 (2002)

3 Summary The transition temperature TC raises, when the substitution rate x increases from 0 to 0.08.A peak of ΔS in the temperature axis shifts to higher temperatures as x increases. This is because TC becomes higher by the larger Co-substitution. The maximum value of ΔS decreases as x increases. This is because the change of magnetization at TC becomes less sharp with the increase of Co content. The value of ΔS is almost close to that of pure Gd. The transition temperature is a little higher than Gd. Thus, the present materials are attractive ones for magnetic refrigerants at the room temperature.