Alexander Barcza

CoMnSi-based metamagnets CoMn 1−x Nix Si
Order of the metamagnetic phase transition
7 %
M 2 (Am 2 /kg) 2
9 %
M 2 (Am 2 /kg) 2
11 %
M 2 (Am 2 /kg) 2
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
20000
18000
16000
14000
12000
330 K
CoMn 0.93 Ni 0.07 Si
70 K
330 K
280 K
250 K
230 K
210 K
190 K
170 K
150 K
130 K
110 K
90 K
70 K
0.00 0.01 0.02 0.03 0.04
µ H/M (T kg/ Am
0
0.05 0.06
2 0
CoMn Ni Si )
0.91 0.09
0.00 0.01 0.02 0.03 0.04 0.05
µ H/M (T kg/Am
0
0.06 0.07
2 10000
330 K
280 K
8000
250 K
230 K
210 K
6000
190 K
170 K
4000
150 K
130 K
2000
110 K
90 K
70 K
0
CoMn Ni Si)
0.89 0.11
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
330 K
10 K
330 K
280 K
250 K
230 K
210 K
190 K
170 K
150 K
130 K
110 K
90 K
70 K
50 K
30 K
10 K
0.00 0.01 0.02 0.03 0.04
µ H/M (T kg/Am
0
0.05 0.06
2 0
)
around phase transitions thermodynamic potentials
can be expanded in a Taylor series with respect
to the order parameter:
Φ = Φ0 + aM 2 + bM 4 − MH
at equilibrium (∂Φ/∂M = 0):
αM + βM 3 = H −→ H
M
= α + βM2
≥ 0, higher order phase transitions
β
< 0, first order phase transitions
Banerjee S K, Phys. Lett. 12 16 (1964)
A Barcza, K G Sandeman (DMG) CoMnSi-based magnetocaloric compounds 14th August 2007 21 / 27