Magnetic anisotropy of nonmodulated Ni-Mn-Ga martensite revisited

摘要

Magnetic anisotropy of single crystal Ni_(50.5)Mn_(30.4)Ga_(19.1) having nonmodulated (NM) martensite structure (c=0.660 nm and b = a=0.547 nm at room temperature) was determined in the range of 10-300 K. The single variant microstructure needed for proper anisotropy determination was prepared by 40 MPa tensile stress in comparison with previous measurements where detwinned microstructure was obtained by compression. The tensile stress process yield the single variant microstructure with easy plane magnetic anisotropy and negligible second anisotropy constant in contrast of two anisotropy constants of the same order for compressed sample. The absolute value of anisotropy constant increases from 2.6 × 10~5 J/m~3 at 300 K to 5 × 10~5 J/m~3 at 10 K.