Transcript 幻灯片 1 - Universiteit van Amsterdam FNWI

Search for magnetic
refrigerant materials
- Lian Zhang
WZI group meeting May 28th 2003, UvA
Outline


What & why is MR?
Search for candidate materials





Gd5(Si,Ge)4
Fe2Mn(Si,Ge)
La(Fe,Si)13
MnFe(P,As)
Conclusion
Fleet
FR de Boer, KHJ Buschow
E Brück, A de Visser, J Klaasse,
YK Huang
O Tegus
AL Wolf
Why magnetic refrigeration?

Conventional gas expansion cooling



Ozone depletion
Global warming
Green MR




Higher efficiency
Less noisy
More compact
Low temperature capability
Magnetic Refrigeration
•
Magnetic-materials change in temperature if subjected to
magnetic-field change
Magnetocaloric effect
S(B,T )  Smag (B,T )  Slat (T )  Sel (T )
B=0
Ericsson
Q
S
Carnot
Q
T
B0
S1
Refrigerant
capacity
S
Sm
Table-like
S2
Tad
T
T2
T1
Integration from isothermal
magnetization curves
Directly measure or
compute from specific heat
measurements
B1 > B2
S
M
B
T1
T
T2
T3
T4
:
:
Tn
Composite material
TC
Field-induced or not,
behaves differently.
Gd5(Si,Ge)4
Hysteresis
M
T
Magnetostructural
transition
Misleading message
50
Gd5Si1.7Ge2.3 Sigle Crystal //a
1T
2T
3T
4T
5T
40
-S (J/kgK)
30
20
10
0
210
220
230
240
250
260
270
280
290
300
310
T (K)
O. Tegus Physica B 319 (2002)
M. Nazih Solid State Comunications 126 (2003)
Fe2Mn(Si1-xGex)

Fe3Si:


Fe2MnSi:




TC > 800 K
TC ~ 250 K
Cubic D03
Heusler-type
Fe3Ge:


D019 (HT)
L12 (LT)
Fe (100)
Ge (111)
Intensity (arb. unit)
Mn
Ge
Mn
0.5 h
Ge
Fe
Ge
1h
2h
D03  D019
4h
10 h
20
30
40
50
60
70
80
2q (Deg)
L. Zhang J. Alloys Comp. 352 (2003)
5.78
5.76
a (Å)
5.74
5.72
5.70
TC - Ge content
5.68
5.66
0.0
0.2
0.4
0.6
0.8
1.0
500
X (Ge content)
400
D019
Para
Lattice change with Ge content
T (K)
300
200
D03
100
0
0.0
0.2
0.4
0.6
x
0.8
1.0
220
x=0.5
440
222
401
004
203
422
220
400
x=0.4
200
002
Intensity (arb. unit)
x=0.2
Intensity (arb. unit)
Observed
202
x=0
201
Fe 2 MnSi1-x Ge x
D0 3
Calculated
x=0.6
Difference
D0 19 +D0 3
x=0.8
30
30
50
40
50
60
70
80
90
60
70
80
90
100
2q (Deg)
D0 19
x=1
20
40
100
2 q (Deg)
L. Zhang Physica B 328 (2003)
3.0
1.2
a
b
2.5
1.0
Disappointed!
1.5
0.6
1.0
0.4
1.5
0.2
0.5
0.0
B=5T
0
50
100
150
200
T (K)
250
-S (J/kg·K)
M (mB/f.u.)
2.0
0.8
300
1.0
350
400
B=2T
0.5
0.0
220
240
260
T (K)
280
300
La(Fe,Si)13



The highest 3d metal
concentration (1:13) in
RT intermetallic
compounds
Failed to be a good
permanent magnet
Cubic: weak
anisotropy
Palstra 1983
Hypothetical LaFe13 structure:
Space group = Fm-3c
Unit cell = 8 f.u. = 112 atoms
= 8 La + 8 FeI + 96 FeII
FeI @8b
FeII @96i
Al, Si
La @8a
Moze 1999
Modification

Substitution of Fe by other transition metals
Mn: failed to get single phase LaFe10.92Mn0.65Si1.43
 Co: LaFe10.92Co0.65Si1.43 has a 2nd transition at TC=265K


Doping with interstitial atoms
B: -Fe emerges in small amount of doping (B=0.2)
 N: difficulty in diffusion makes sample inhomogeneous

and broadens the transition enormously

C: saturated at C=0.5, while TC=250K
5K
2.0
235 K
1.0
16
2T
5T
14
12
0.5
-S (J/kgK)
M (mB/Fe or Co)
1.5
0.0
0
1
10
300 K
8
6
2
3
4
5
B (T)4
2
0
220
230
240
250
260
270
T (K)
280
290
300
310
1.8
Field step 0.1T
1.6
1.4
1.4
1.2
1.2
1.0
1.0
mB/Fe
mB/Fe
1.6
1.8
0.8
Field step 0.005T
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
0.0
0.0
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
B (T)
B (T)
1.8
0.2
Field step 0.02T
1.6
1.4
mB/Fe
1.2
Be cautious with the height of
S peak when it is a 1st order
field-induced transition.
1.0
0.8
0.6
0.4
0.2
0.0
0.0
0.2
0.4
0.6
0.8
1.0
B (T)
1.2
1.4
1.6
1.8
2.0
2.0
For the field-induced 1st order transition, the field-up S-T show
point rotation symmetry with the field-down S-T curve.
60
40
-S
20
0
-20
-40
186
188
190
T (K)
192
194
196
MnFe(P,As)
T(K)
ms
400
ms
(mB/f.u.)
TN
4
TN
TC
3
300
AF
200
TN
AF
2
F
AF
100
1
Orth
MnFeP
Hex
Tetr
MnFeAs
Beckman-Lundgren, 1991
O. Tegus Physica B 319 (2002)
0.20
0.10
Virgin effect
2.0
0.05
B = 0.01T
1.5
270 K
0.00
0
50
100
150
T (K)
200
mB/f.u.
mB/f.u.
0.15
250
Field up
Field down
300
1.0
275 K
0.5
280 K
0.0
0
1
2
3
B (T)
4
5
Intensity
c
b
a
46
48
50
52
54
c
56
2qdeg.)
mB/f.u.
44
b
a
B = 0.01T
0
50
100
150
200
T (K)
250
300
350
400
3.5
X=0.4
X=0.2
3.0
mB/f.u.
2.5
2.0
1.5
1.0
B = 2T
sweep rate: 2K/min
0.5
0.0
200
220
240
260
280
300
T (K)
320
340
360
380
400
3.5
X=0.2
3.0
2.5
1.5
30
1.0
X=0.4
25
0.5
0.0
0
1
2
3
B (T)
-S (J/kgK)
mB/f.u.
2.0
X=0.2
20
15
10
4
5
2T
5T
5
0
240
260
280
300
320
T (K)
340
360
380
Conclusion





Materials for MR are ready
Much room for improvement
Behaviors vary: rich ingredients
Theories are called
Accommodate engineering challenges