The field and temperature dependence of the magnetic and structural properties of the shape memory compound Ni1.84Mn1.64In0.52

Magnetization and high resolution neutron powder diffraction measurements have been made on the magnetic shape memory alloy Ni1.84Mn1.64In0.52. The compound undergoes a broad structural phase transition, which on heating starts at similar to 150 K and finishes at similar to 215 K. On cooling there is a similar to 20 K hysteresis. The high temperature parent phase is cubic (a = 5.988 angstrom) with the L2(1) structure in which the excess Mn atoms occupy the vacancies on the Ni and In sites. The magnetic moment is located mainly on the Mn atoms with the same magnitude on both the 4a (Mn) and 4b (In) sites. The low temperature martensite is monoclinic with parameters a = 4.405(2), b = 5.553(2), c = 12.950(2) angstrom, beta = 86.47(10)degrees and space group P2/m. The magnetic properties of the martensitic phase are complex and indicate metamagnetic behaviour.