Martensitic transition, structure and magnetic anisotropy of martensite in Ni-Mn-Sn single crystal

Abstract

The structural and magnetic properties of Ni50Mn37.5Sn12.5 single crystal were investigated. The alloy undergoes martensitic transformation at 308 K from the austenite phase to the structurally modulated tetragonal 4M martensite phase with lattice parameters a4M = 6.177 Å, c4M = 5.669 Å. The alloy shows 7.9% pre-strain upon uniaxial compression along the 〈001〉 direction, which is near the theoretical 8.2% maximum twinning strain. Magnetization measurements reveal that the magnetic anisotropy of the martensite phase is uniaxial with the easy magnetization axis corresponding to the shortest c axis of the tetragonally distorted unit cell, while its a axis is the hard magnetization direction. The magnetic anisotropy constant Ku saturates at low temperature around 7 × 104 J/m3 and then gradually decreases with increasing temperature as the system approaches the Curie temperature of martensite at 215 K.