Effect of changing P/Ge and Mn/Fe ratios on the magnetocaloric effect and structural transition in the (Mn,Fe) (P,Ge) intermetallic compounds

P. Wlodarczyk; L. Hawelek; P. Zackiewicz; M. Kaminska; A. Chrobak; A. Kolano-Burian

Open Access

Effect of changing P/Ge and Mn/Fe ratios on the magnetocaloric effect and structural transition in the (Mn,Fe)₂ (P,Ge) intermetallic compounds

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| Sep 08, 2016

Materials Science-Poland

Volume 34 (2016): Issue 3 (September 2016)

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Published Online: Sep 08, 2016

Page range: 494 - 502

Received: Jul 13, 2015

Accepted: May 24, 2016

DOI: https://doi.org/10.1515/msp-2016-0068

Keywords
magnetocaloric effect, FeP type compounds, phase transition

© 2016 P. Wlodarczyk et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Microstructure of sample 1 and its local elemental analysis. In the description a. 1 and a. 2 stand for areas and p. 3 and p. 4 for points.

Ambient temperature X-ray diffraction patterns.

Rietveld refinement pattern for Sample 1. Red points – experimental data, solid black line – refined curve, vertical lines define the Bragg line positions separately for each phase, upper blue line marks the difference between the experimental and refined data.

Temperature dependent X-ray diffraction maps: (a) Sample 1 (b) Sample 3 and (c) Sample 5.

Arrott plots and magnetic entropy change for Samples 5, 1 and 3 (numbered from the top)

Impact of Ge/P and Mn/Fe ratios on adiabatic temperature change and thermal hysteresis of studied samples.

Complex analysis of structural transition kinetics in Samples 1 and 3 with different Ge/P ratios. Top panel – DSC curves for different heating rates, middle panel – Avrami fits of kinetic curves, bottom panel – FWO fits and activation energies.

Comparison of the obtained data with the literature.

Chemical composition	T_C [K]	−DS : B	Preparation method	Year
Mn_1.1Fe_0.9P_0.81Ge_0.19	260	14 J/kg K : 2 T	bulk (mechanical alloying)	2008[4]
Mn_1.1Fe_0.9P_0.78Ge_0.22	298	20 J/kg K : 2 T
Mn_1.1Fe_0.9P_0.75Ge_0.25	330	13 J/kg K : 2 T
Mn_1.1Fe_0.9P_0.8Ge_0.2	206	15 J/kg K : 2 T	ribbon bulk alloy (induction) ribbon	2006[5]
Mn_1.1Fe_0.9P_0.76Ge_0.24	299	11 J/kg K : 2 T
Mn_1.1Fe_0.9P_0.76Ge_0.24	317	17 J/kg K : 2 T
Mn_1.1Fe_0.9P_0.8Ge_0.2	255	28 J/kg K : 2 T	bulk (mechanical alloying)	2009[6]
Mn_1.1Fe_0.9P_0.8Ge_0.2	250	22 J/kg K : 2 T	bulk (mechanical alloying)	2010[7]
MnFeP_0.7Ge_0.3	360	−	bulk (mechanical alloying)	2004[8]
MnFeP_0.5Ge_0.5	570
Mn_1.1Fe_0.9P_0.74Ge_0.26	323	45 J/kg K : 5 T	ribbons (arc melting + melt spinning)	2015[9]
Mn_1.1Fe_0.9P_0.7Ge_0.3	360	19 J/kg K : 5 T
Mn_1.1Fe_0.9P_0.68Ge_0.32	403	9 J/kg K : 5 T
Mn_1.1Fe_0.9P_0.7Ge_0.3	380	−	bulk (mechanical alloying)	2005[10]
Mn_1.15Fe_0.85P_0.76Ge_0.25	263	10 J/kg K : 2 T	bulk (arc melting)	2015[11]
Mn_1.15Fe_0.85P_0.74Ge_0.26	272	−
Mn_1.15Fe_0.85P_0.72Ge_0.28	314	−
Mn_1.15Fe_0.85P_0.70Ge_0.30	330	12 J/kg K : 2 T
Mn_1.15Fe_0.85P_0.68Ge_0.32	342	12 J/kg K : 2 T
Mn_1.05Fe_0.95P_0.81Ge_0.19	295	9 J/kg K : 2 T	bulk (solid-state reaction)	this work
Mn_1.05Fe_0.95P_0.79Ge_0.21	310	−
Mn_1.05Fe_0.95P_0.78Ge_0.22	335	7 J/kg K : 2 T
Mn_1.1Fe_0.9P_0.78Ge_0.22	318	−
Mn_1.17Fe_0.83P_0.78Ge_0.22	293	9 J/kg K : 2 T

Peak temperatures and Avrami kinetic parameters derived for two measured samples with different heating rates. F – rate of heating, Tp – peak transformation temperature, ln(k’) – rate constant logarithm, n – Avrami exponent, t1/2 – half-time of transformation.

Φ [K/min]	T_p [K]	ln(k’)	n	t_1/2 [min]
Mn_1.05Fe_0.95P_0.78Ge _0.22
30	342.48	(8.59±0.27) × 10⁻²	4.31±0.11	0.900
25	342.33	7.38±0.28) × 10⁻²	4.26±0.12	0.902
20	341.85	(5.60±0.30) × 10⁻²	4.07±0.12	0.901
15	341.71	(−4.31±2.47) × 10^⁻³	4.24±0.13	0.918
10	341.57	(−2.11±0.07) × 10^⁻¹	4.38±0.16	0.965
5	340.79	− 1.01±0.04	4.46±0.19	1.155
Mn_1.05Fe_0.95P_0.81Ge _0.19
30	305.27	(3.37±0.09) × 10⁻²	5.24±0.08	0.926
25	304.98	(2.10±0.50) × 10⁻²	5.18±0.12	0.928
20	304.64	(−5.37±0.10) ×10^⁻²	5.27±0.11	0.942
15	304.30	(−1.41±0.03) × 10^⁻¹	4.87±0.11	0.955
10	303.90	(−4.71±0.10) × 10^⁻¹	5.25±0.12	1.020
5	303.28	−1.66±0.04	−5.27±0.13	1.278

Weight fractions of refined phases, room temperature lattice parameters, c/a ratio and unit-cell volume for Fe2P-type phase. Sample 3 is in the low-temperature ferromagnetic state.

No.	Fe₂P-type [%]	MnO [%]	Fe₃Mn₄Ge₆[%]	a = b [Å]	c [Å]	c/a ratio	V[ Å³]
1	87.97±0.74	6.45±0.53	5.57±0.17	6.0795±0.0006	3.4515±0.0004	0.5677	110.476±0.021
2	87.53±1.03	6.57±1.14	5.90±0.32	6.1016±0.0014	3.4421±0.0010	0.5641	110.979±0.049
3	83.05±1.07	12.20±0.97	4.75±0.21	6.1765±0.0011	3.3514±0.0006	0.5426	110.724±0.034
4	80.97±1.04	12.45±0.98	6.58±0.22	6.1038±0.0009	3.4441±0.0006	0.5704	111.123±0.030
5	81.83±1.39	14.24±0.93	3.93±0.18	6.1118±0.0008	3.4429±0.0005	0.5633	111.375±0.027

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Effect of changing P/Ge and Mn/Fe ratios on the magnetocaloric effect and structural transition in the (Mn,Fe)₂ (P,Ge) intermetallic compounds

Article Category: Research Article

Published Online: Sep 08, 2016

Page range: 494 - 502

Received: Jul 13, 2015

Accepted: May 24, 2016

DOI: https://doi.org/10.1515/msp-2016-0068

Keywords
magnetocaloric effect, FeP type compounds, phase transition

© 2016 P. Wlodarczyk et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Comparison of the obtained data with the literature.

Peak temperatures and Avrami kinetic parameters derived for two measured samples with different heating rates. F – rate of heating, Tp – peak transformation temperature, ln(k’) – rate constant logarithm, n – Avrami exponent, t1/2 – half-time of transformation.

Weight fractions of refined phases, room temperature lattice parameters, c/a ratio and unit-cell volume for Fe2P-type phase. Sample 3 is in the low-temperature ferromagnetic state.

Effect of changing P/Ge and Mn/Fe ratios on the magnetocaloric effect and structural transition in the (Mn,Fe)2 (P,Ge) intermetallic compounds

Article Category: Research Article

Published Online: Sep 08, 2016

Page range: 494 - 502

Received: Jul 13, 2015

Accepted: May 24, 2016

DOI: https://doi.org/10.1515/msp-2016-0068

Keywordsmagnetocaloric effect, FeP type compounds, phase transition

© 2016 P. Wlodarczyk et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Comparison of the obtained data with the literature.

Peak temperatures and Avrami kinetic parameters derived for two measured samples with different heating rates. F – rate of heating, Tp – peak transformation temperature, ln(k’) – rate constant logarithm, n – Avrami exponent, t1/2 – half-time of transformation.

Weight fractions of refined phases, room temperature lattice parameters, c/a ratio and unit-cell volume for Fe2P-type phase. Sample 3 is in the low-temperature ferromagnetic state.

Effect of changing P/Ge and Mn/Fe ratios on the magnetocaloric effect and structural transition in the (Mn,Fe)₂ (P,Ge) intermetallic compounds

Keywords
magnetocaloric effect, FeP type compounds, phase transition