- Lian Zhang

Search for magnetic refrigerant materials

WZI group meeting May 28WZI group meeting May 28thth 2003, UvA 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

)()(),(),( TSTSTBSTBS ellatmag

S

T

B0

B=0

Ericsson

Q

Q

Carnot

T1T2

S2

S1

Sm

Tad

Refrigerant capacity

Table-like

S

T

Integration from isothermal magnetization curves

Directly measure or compute from specific heat measurements

T

SB

M B1 > B2

T1

T2

T3

T4

:

:

Tn

Composite materialTC

Field-induced or not, Field-induced or not, behaves differently. behaves differently.

GdGd55(Si,Ge)(Si,Ge)44

Magnetostructural Magnetostructural transitiontransition

MM

TT

Hysteresis

Misleading messageMisleading message

M. Nazih Solid State Comunications 126 (2003)

210 220 230 240 250 260 270 280 290 300 310

0

10

20

30

40

50

Gd5Si

1.7Ge

2.3 Sigle Crystal //a

1T 2T 3T 4T 5T

T (K)

-S

(J/

kgK

)

O. Tegus Physica B 319 (2002)

Fe2Mn(Si1-xGex)

Fe3Si: TC > 800 K

Fe2MnSi: TC ~ 250 K

Cubic D03

Heusler-type

Fe3Ge: D019 (HT)

L12 (LT)

20 30 40 50 60 70 80

Inte

nsity

(ar

b. u

nit)

10 h

4 h

2 h

1 h

0.5 h GeFeGeMn

Ge

Fe (100)

Mn

Ge (111)

2 (Deg)

L. Zhang J. Alloys Comp. 352 (2003)

D03 D019

0.0 0.2 0.4 0.6 0.8 1.00

100

200

300

400

500

D019

D03

Para

T (

K)

x

0.0 0.2 0.4 0.6 0.8 1.0

5.66

5.68

5.70

5.72

5.74

5.76

5.78

a

(Å

)

X (Ge content)

Lattice change with Ge content

TC - Ge content

20 30 40 50 60 70 80 90 100

D019

D019

+D03

D03

Fe2MnSi

1-xGe

x

x=1

x=0.8

x=0.6

x=0.5

x=0.4

x=0.2

x=0

In

ten

sit

y (

arb

. u

nit

)

2 (Deg)

30 40 50 60 70 80 90 100

440

422

400

220

00440

1222

203

220

202

201

002

200

Difference

Calculated

Observed

Inte

nsity

(ar

b. u

nit)

2 (Deg)

L. Zhang Physica B 328 (2003)

0 50 100 150 200 250 300 350 4000.0

0.2

0.4

0.6

0.8

1.0

1.2

a

M

( B

/f.u

.)

T (K)

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

b

M ( B

/f.u

.)

T (K)

220 240 260 280 3000.0

0.5

1.0

1.5

B=2T

B=5T

-S

(J/

kg·K

)

T (K)

Disappointed!

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

FeI @8b

FeII @96i

La @8a

Hypothetical LaFe13 structure:

Space group = Fm-3c

Unit cell = 8 f.u. = 112 atoms

= 8 La + 8 FeI + 96 FeII

Al, Si

Moze 1999

Modification

Substitution of Fe by other transition metalsMn: failed to get single phase LaFe10.92Mn0.65Si1.43 Co: LaFe10.92Co0.65Si1.43 has a 2nd transition at TC=265K

Doping with interstitial atomsB: -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

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

B/F

e

B (T)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

B/F

e

B (T)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

B/F

e

B (T)

Field step 0.1T

Field step 0.02T

Field step 0.005T

Be cautious with the height of S peak when it is a 1st order field-induced transition.

186 188 190 192 194 196

-40

-20

0

20

40

60

-

S

T (K)

For the field-induced 1st order transition, the field-up S-T show point rotation symmetry with the field-down S-T curve.

MnFe(P,As)

MnFePMnFeP MnFeAsMnFeAs

TT(K)(K)

400

300

200

100OrthOrth

AFAF

TTNN

TTNN

AFAF

TTCC

FF

TetrTetrHexHex

TTNN

ss

((BB/f.u.)/f.u.)ss

4

3

2

1

AFAF

Beckman-Lundgren, 1991Beckman-Lundgren, 1991

O. Tegus Physica B 319 (2002)

Virgin effectVirgin effect

44 46 48 50 52 54 56

In

tens

ity

2deg.)

c

b

a

a

b

c

X=0.4X=0.4 X=0.2X=0.2

X=0.2

X=0.2

X=0.4

Conclusion

Materials for MR are ready Much room for improvement Behaviors vary: rich ingredients Theories are called Accommodate engineering challenges