Influence of the Magnetic Anisotropy on the Magnetic Entropy Change of ${\rm Ni}_{2}{\rm Mn}({\rm Ga},{\rm Bi})$ Memory Shape Alloy

Abstract

The magnetocaloric effect (MCE) is a good chance to create a more efficient refrigeration technique, both in energy and environmental friendliness. On the search for materials with large MCE (mainly characterized by a great magnetic entropy variation) in a wide temperature range around room temperature, this work focuses on the widely studied Heusler alloy and the influence of bismuth alloying in the stoichiometry Ni 2 MnGa in an attempt to make the magnetic and structural transition temperatures, T C and T M , come closer, and therefore create a large MCE. In addition, we discuss the influence of alloying processes on the magnetic anisotropy. Our results have in fact increased T M and decreased T C , but Bi substitution in Ga site (from 0 up to 5%) has been insufficient to merge those two transitions. The maximum magnetic entropy change was found to be 3.8 J/kg.K for the pure sample (without Bi) and 2.2 J/kg.K for sample 4 (maximum Bi concentration).Index Terms-Heusler alloy, magnetocaloric effect, memory shape, Ni 2 MnGa.

Experimental evidences of enhanced magnetocaloric properties at room temperature and half-metallicity on Fe 2 MnSi-based Heusler alloys

“…It is therefore possible to create a thermomagnetic cycle and a magnetic refrigerator based on these processes [14,15]. Some compounds that exhibit remarkable MCE potentials are, for instance, manganites [16][17][18][19]; MnAs-based compounds [20][21][22][23]; Heusler alloys [10,11]; La-Fe-Si alloys [24,25]; intermetallics like RNi 2 (R = Nd, Gd, Tb) [26], RCo 2 (R = Er, Tb) [27] and PrNi 1−x Co x [28]; and even diamagnetic materials like graphenes [29,30].…”