Phase transition temperatures and magnetic entropy change in Ni-Mn-In-B based Heusler alloys

One of the aspects of great attention of Heusler alloys is the large value of magnetic entropy change ($\Delta $S$_{M})$ and their possible application as a working material in magnetocaloric effect based magnetic refrigerators. It was reported earlier that Ni$_{50}$Mn$_{34.8}$In$_{15.2}$ has first order martensitic transition temperature T$_{M}\approx $ 212K, Curie temperature of austenitic phase T$_{C}\approx $ 328K and $\Delta $S$_{M}$ value associated with T$_{M}$ and T$_{C}$ are respectively 13 and -7 J/kg K [1]. In the present study, we are reporting the effect of partial substitution of In by B in Ni$_{50}$Mn$_{34.8}$In$_{15.2}$ by AC susceptibility, thermal expansion, and magnetization measurements. We observed that substitution of boron sharply increase T$_{M,}$ and significantly enhance the $\Delta $S$_{M}$ peak value higher than 30 J/kg K at T$_{M}\approx $ 296K; however the $\Delta $S$_{M}$ value remains almost same at T$_{C}$. Therefore, the Ni-Mn-In-B based Heusler alloys will be potential material for the study of room temperature magnetic refrigerator materials. Reference: [1] A. K. Pathak, M. Khan, I. Dubenko, S. Stadler, and N. Ali, Appl. Phys. Lett. \textbf{90}, 262504 (2007).