Magnetocrystalline Anisotropy in a Single-Variant Co-Ni-Al Ferromagnetic Shape Memory Alloy

Abstract

The single-variant state and the magnetocrystalline anisotropy in a single crystal Co41Ni32Al27 ferromagnetic shape memory alloy (FSMA) have been investigated. After applying compressive stress, the single-variant state was confirmed by optical micrograph and linear thermal expansion measurements. In the heating process for the single-variant martensite phase, the shrinkage of about 7% takes place at the reverse transformation temperature. From the magnetization curves along the c-, a-axes and the [110]M directions in the single-variant state, the c-axis is determined to be the hard axis and the magnetocrystalline anisotropy constant in the single crystal Co41Ni32Al27 β′ martensite phase is evaluated to be 3.2×105 J/m3 at 5 K.