Mahmud Khan

The first-order phase transition and associated magnetocaloric properties of Mn0.5Fe0.5Ni0.95Cr0.05Si0.95Al0.05 have been studied by x-ray diffraction and dc magnetization measurements. The diffraction data for the sample showed that both the orthorhombic and hexagonal crystalline phases coexisted at room temperature. The temperature dependence of magnetization was measured at a constant field of 0.2 T. The first-order phase transition was observed at 325 K during heating and at 306 K during cooling, showing a thermomagnetic hysteresis of 19 K. For magnetic field change of 5 T, the entropy changes evaluated from the isothermal magnetization data peaked at 322 K during warming and at 313 K during cooling, showing a thermomagnetic hysteresis of 9 K. This difference in the magnitude of the thermomagnetic hysteresis was attributed to the virgin effect due to stress and crack formation during the first cooling from hexagonal to orthorhombic phase. Peak entropy changes of −16 J kg−1 K−1 and −42 J kg−1 K−1 were observed on heating for field changes of 2 and 5 T, respectively. The related refrigeration capacities were 74 J/kg (2 T) and 194 J/kg (5 T).