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

摘要

Magnetostriction of a non-modulated martensite was measured for Ni2.27Mn0.73Ga ferromagnetic shape memory alloy in steady magnetic fields mu H-0 up to 10 T at temperatures below room temperature and in mu H-0 = 1 T at temperatures above room temperature. Linearity of the longitudinal magnetostriction lambda(parallel to) observed at high fields mu H-0 6 T implies that the magnetostriction is associated with a 3d electron band. The anisotropic magnetostriction obtained in a magnetic field mu H-0 = 1 T at T = 4.2 K is similar to 16 ppm and decreases down to 3 ppm with the increase in temperature. The volume magnetostriction is positive but very small (similar to 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 alpha of Ni2.27Mn0.73Ga in the martensitic state was measured to be alpha similar to 13 x 10(-6) K-1 which is comparable with the thermal expansion coefficient of a non-stoichiometric Ni2.19Mn0.81Ga single crystal. (c) 2018 Elsevier B.V. All rights reserved.