Study on iron-rich (Mn,Fe)1.95(P,Si) magneto-caloric material Z.Q. Ou, L. Zhang, H.D. Nguyen, A.J.E. Lefering, J.C. Vieira Leitao, E. Brück
Fundamental Aspects of Materials and Energy (FAME), Faculty of Applied Sciences (TNW), TU Delft (TUD) 180
Motivation is defined as heating or cooling a magnetic material by exposing the material to
Mn1.95-xFexP0.66Si0.34
1T
160
Magneto-caloric effect, couples the magnetic moments to the lattice,
x=1.0 x=1.1 x=1.2 x=1.3 x=1.4 x=1.5
140
a changing magnetic field.
2
Applications: Magnetic Refrigeration:[1] - High efficiency - Environmentally friendly Power Generation:[2] - High efficiency - Waste heat to power
4.5 4.0
100
3.5
80
3.0 M (µ B/f.u. )
M (Am /Kg)
120
x=1.0 x=1.1 x=1.2 x=1.3 x=1.4 x=1.5
2.5
60 40
2.0 1.5 1.0
20
Fe2P-based (Mn,Fe)2(P,Si) materials: Large magneto-caloric effect Large working temperature range Cheap materials
0 50
B(T)
0.5 0 0.0
1
2
100
3
4
150
5
200
250
300
350
400
T (K) Fig. 2 Temperature dependence of the magnetization of Mn1.95-xFexP0.66Si0.34 measured in a field of 1 T. The insert shows the M-B curves measured at 5 K.
Problems: Large thermal hysteresis Impurity phase (Mn,Fe)3Si
• Tc can be adjusted by changing the Mn/Fe ratio • ∆Thys can be reduced by increasing Fe concentration • Saturation magnetization at 5 K decreases with increasing Fe content
Experimental results
120
120
(a)
Off-stoichiometric composition
x = 1.20
100
x = 1.40
(c)
269 K
100
Ball-milling technology
20 0
315 K
20
305 K
15
1
2
B (T)
3
4
30
-∆ Sm (J/kgK)
35
40
45 2θ (degree)
50
002
211
300
210
173 K
201
111
255 K
60
Fig.1 Temperature dependent X-ray diffraction patterns of Mn0.75Fe1.20P0.66Si0.34. The arrows indicate the coexistence of FM and PM phases. • Crystallizes in Fe2P-type hex. structure
5
20
∆T = 2 T ∆T = 1 T
5
6
290
0.5
1.0
B (T)
1.5
2.0
(d)
2.5
x = 1.40
3 ∆T = 2 T ∆T = 1 T
2
1
T (K)
T (K) 280
400 K
0 0.0
x = 1.20
10
0 270
55
40
4
(b)
298 K
60
320 K 0
∆ T=5K
40
2 M (Am /Kg)
60
335 K
Intensity(arb.unit)
80
∆ T=3K
395 K
80
-∆ Sm (J/kgK)
2 M (Am /Kg)
280 K
Temperature
300
310
320
0 280
300
320
340
360
380
400
Fig .3 Magnetization curves of Mn1.95-xFexP0.66Si0.34 (x = 1.20 (a) and x = 1.40 (c)) in the vicinity of their Curie temperatures and the magnetic entropy changes (x = 1.20 (b) and x = 1.40 (d)) for different magnetic field changes. • Field induced transition is observed (x = 1.2), but is depressed with higher Fe content (x = 1.4) • Large -∆SM is obtained on Iron-rich (Mn,Fe)1.95(P,Si) compounds, but the value is strongly reduced with further increasing Fe concentration
• No (Mn,Fe)3Si impurity phase is observed
Conclusions:
References & Acknowledgements
Single phase sample is obtained by using ball-milling technology.
[1] V. K. Pecharsky, K. A. Gschneidner Jr., Phys. Rev. Lett. 78, 4494 (1997).
Thermal hysteresis decreases with increasing Fe concentration.
[2] E. Brück, O. Tegus and K. Buschow, INTERMAG 2006, IEEE International, P85. The authors would like to thank FOM and BASF for the financial support.
Email:
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For the iron-rich (Mn,Fe)1.95(P,Si) compounds, the Mn:Fe and/or P:Si ratio(s) still need to be optimized.
Delft Days on Magnetocalorics October 24–25 2011