Temperature Dependence of Rearrangement of Martensite Variants in a Ferromagnetic Shape Memory Alloy Ni_2MnGa

摘要

We have investigated temperature dependence of rearrangement of martensite variants under magnetic field in a stoichiometric Ni_2MnGa. When a magnetic field is applied along [001]_P direction at a temperature below its transformation temperature of 202 K, multi-variant state changes to the single variant state whose c axis (easy axis) lies along the field direction. To explain the rearrangement of variants, the magnetic shear stress acting across the twinning plane (τ_(mag)) was evaluated from magnetocrystalline anisotropy constant, and was compared with the stress required for the rearrangement of variants (τ_(teq)) obtained compressive tests. For all the temperatures examined, the maximum of τ_(mag) is sufficiently larger than τ_(req).