Magnetic refrigerant
Magnetic character change in compounds La(Fe Co ) Si
1-x
Soichiro Sasaki
Suzuki Kusakabe lab.
x
11.2
1.8
Contents
• 1 Introduction
• 2 magnetic character of compounds
La(Fe Co ) Si
• 3 Summary
1-x
x
11.2
1.8
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
Gas refrigerant
generation of heat
compression
Magnetic refrigerant
generation of heat
expanding
Adding a
magnetic field
absorption of heat
Reducing a magnetic field
absorption of heat
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）
Q  T1  S M
Q  S  0
（H １ ＞H ２ ）
(A→B)
(B→C)
1-4 the necessary factor of
magnetic refrigerant
S ( H , T )  
H
0
 M

 T

dH 

To get big ΔS
Maxwell equation
・High magnetization
・Soft ferromagnetism
ex. Compound of Gd or Dy
 S   M 
  

 B T  T  B
The structure of compound La(Fe
Co Si )
x
ｙ
1-x-ｙ
13
(Co)
(Co)
Cubic NaZn13a-type structure
Cluster of
Icosahedron
(20面体）
1/8 unit sell
Top view of 1/8
unit sell
Magnetic character of compounds
La(Fe Si )
x
La(Fe0.88Si0.12 )13
1-x 13
La(Fe0.86Si0.14 )13
A. Fujita, Y. Akamatsu and K. Fukamichi. J. Appl. Phys. 85 (1999), p. 4756
Character of compounds
La(Fe Si )
x
1-x 13
S. Fujieda, A. Fujita, and K. Fukamichi
Applied Physics Letters -- August 12, 2002 -- Volume 81, Issue 7, pp. 1
Magnetizatic entropy change and
its temperature variation in
compounds La(Fe Co ) Si
1-x
x
11.2
1.8
F. X. Hu, X. L. Qian, et al. J. Appl.
Phys. 92, 3620 (2002)
Magnetization-Temperature graph
H=0.01T
F. X. Hu, X. L. Qian, et al. J. Appl. Phys. 92, 3620 (2002)
Magnetization-Magnetic field graph
F. X. Hu, X. L. Qian, et al. J. Appl. Phys. 92, 3620 (2002)
Entropy-temperature graph
S ( H , T )  
H
0
 M 
 dH 
 T 
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.

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