Abstract
The influence of partial substitution of mischmetal on the structure, Curie temperature and magnetocaloric effect has been investigated in La1-xMxFe11.5Si1.5 alloys. X-ray diffraction patterns indicate the alloys crystallize mainly in NaZn13-type cubic structure and the amount of secondary α-Fe phase obviously reduces in the mischmetal doped alloys. As the content of mischmetal increases, the Curie temperature is reduced from 198.1 K for x = 0 to 184.2 K for x = 0.3 and the thermal hysteresis is enlarged from 3.5 K for x = 0 to 8.2 K for x = 0.3. Upon a field change from 0 to 3 T, the obtained maximum isothermal entropy change values are 17.2, 19.8, 37.8 and 47.9 J/kgK for x = 0, 0.1, 0.2 and 0.3, respectively. The entropy changes due to the latent heat of first-order transitions are estimated to be 11.3, 14.7, 18.5 and 23.4 J/kgK for x = 0, 0.1, 0.2 and 0.3, respectively. The enhancement of giant magnetocaloric MCE in La1-xMxFe11.5Si1.5 alloys originates from the strengthened itinerant electron metamagnetic transitions by adding the mischmetal. Our result suggests that the mischmetal doped NaZn13-type La-Fe-Si alloys are potential candidates of refrigerants for magnetic refrigeration.
Highlights
Comparing to the refrigerator based on gaseous compression and expansion, magnetic refrigeration utilizing the magnetocaloric effect (MCE) of magnetic material shows some advantages, such as high efficiency, environmental friendliness and low noise
Fujita et al reported that the partial substitution of Ce for La resulted in a decrease of the Curie temperature (TC) and an increase of isothermal entropy change (∆ST ).[8]
The enhancement of the MCE in La1-xMxFe11.5Si1.5 alloys should be ascribed to the strengthened field-induced itinerant electron metamagnetic (IEM) transition by adding the mischmetal, similar to that observed in pure Ce doped alloys.[8,9,11]
Summary
The structural, magnetic and magnetocaloric properties of the mischmetal doped alloys were investigated
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