Magnetostructural transition and large magnetocaloric effect in (Mn_(0.6)Fe_(0.4)) NiSi_(1-x)Al_x (x = 0.06-0.08) alloys

摘要

First order coupled magnetostructural transition (MST) between ferromagnetic orthorhombic and paramagnetic hexagonal structure and large magnetocaloric effect are reported in the present article in transition metal based Al doped (Mn_(0 6)Fe_(0.4))NiSi_(1-x)Al_x (x = 0.06, 0.07) alloys. On doping Al in place of Si, the structural transition temperature is found to shift to around room temperature (～272 K for x = 0.07) from a high temperature of —1210 K for MnNiSi system. On further increase in Al doping with x = 0.08, only magnetic transition is observed at —145 K. Isothermal magnetic entropy change (△S_M) as large as —20.6 Jkg~(-1)K~(-1) is found for the alloy with x = 0.07 due to a change of 50 kOe magnetic field. Large value of ASM observed near room temperature for the alloy with x = 0.07 enable it as a potential candidate for magnetic refrigerant.