Magnetostriction of ferromagnetic shape memory alloy Ni2.27Mn0.73Ga studied in magnetic fields up to 10 T

Abstract Magnetostriction of a non-modulated martensite was measured for Ni 2.27 Mn 0.73 Ga ferromagnetic shape memory alloy in steady magnetic fields μ 0 H up to 10 T at temperatures below room temperature and in μ 0 H  ≤ 1 T at temperatures above room temperature. Linearity of the longitudinal magnetostriction λ || observed at high fields μ 0 H  > 6 T implies that the magnetostriction is associated with a 3 d electron band. The anisotropic magnetostriction obtained in a magnetic field μ 0 H  = 1 T at T  = 4.2 K is ∼16 ppm and decreases down to 3 ppm with the increase in temperature. The volume magnetostriction is positive but very small (∼0.6 ppm) under these conditions. In the region of the magnetostructural phase transition the longitudinal and volume magnetostriction showed a complex sigh-changing behavior which depends on the strength of applied magnetic field. Thermal expansion coefficient α of Ni 2.27 Mn 0.73 Ga in the martensitic state was measured to be α ∼13 × 10 −6  K −1 which is comparable with the thermal expansion coefficient of a non-stoichiometric Ni 2.19 Mn 0.81 Ga single crystal.