Effect of Bi substitution on the magnetic and magnetocaloric properties of Ni50Mn35In15-xBix Heusler alloys

The structural, magnetic, magnetocaloric, and transport properties of Ni50Mn35In15-xBix (x = 0, 0.25, 0.5, 1, 1.5) compounds has been studied through X-ray diffraction (XRD), differential scanning calorimetry, and magnetization measurements. A mixture of high temperature austenite phase (AP) and low temperature martensitic phase (MP) was observed from the XRD at room temperature. The saturation magnetization M-S at 10 K was found to decrease with increasing Bi content. A shift in the martensitic transition temperature (T-M) relative to the parent compound was observed with a maximum shift of similar to 36 K for x = 1.5. Abnormal shifts in TC and TM to higher temperatures were observed at high field for x >= 0.5. Large magnetic entropy changes (Delta S-M) of about 40 J/kg K (x = 0) and 34 J/kg K (x = 0.25) were observed at T-M with H = 5 T, which reduced significantly for higher Bi concentrations. The doping of small amounts of Bi in the In sites increased the peak width of the Delta S-M curves at the second order transition, leading to larger values of relative cooling power. A significant magnetoresistance (-30%) was observed near TM with Delta H = 5T for x = 0.5. (C) 2017 Author(s).