Neutron diffraction studies on the Heusler alloy Ni<inf>50</inf>Mn <inf>37</inf>Sb<inf>13</inf>

The evolution of martensitic to austenitic transformation in Ni 50Mn37Sb13 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 B/Mn in Mn (2a and 2f) sites. © 2011 American Institute of Physics.