Neutron diffraction studies on the Heusler alloy Ni50Mn37Sb13

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The evolution of martensitic to austenitic transformation in Ni50Mn37Sb13 has been studied usingtemperature dependent neutron diffraction, thermal property, and magnetization studies. Differential scanning calorimetric studies reveal a martensitic transformation TM around 291 K. The magnetization data yield a ferromagnetic ordering temperature of 329 K in the austenitic phase and 230 K in the martensitic phase. The analysis of the powder neutron diffraction data in the temperature range of 325–12 K indicates a structural transition from a high temperature cubic L21 type structure to an orthorhombic structure. At 270 K, both cubic and orthorhombic phases coexist. Anisotropic unit cell changes are observed at the martensitic transformation: The unit cell expands by about 1.5% along the a axis, by about 2.5% along the c axis, and compresses by about 4.28% along the b axis. Both cubic and orthorhombic phases show commensurate collinear ferromagnetic ordering with a magnetic moment of ∼3.67 μB/Mn in Mn (2a and 2f) sites.