Observation of Reverse Transformation in Metamagnetic Shape Memory Alloy Ni₄₀Co₁₀Mn₃₄Al₁₆ by High-Field X-Ray Diffraction Measurements

Abstract

The structural properties of metamagnetic shape memory alloy Ni₄₀Co₁₀Mn₃₄Al₁₆ were investigated by X-ray powder diffraction measurements in the temperature range from 283 to 473 K and magnetic fields up to 5 T. With increasing temperature from 283 K, the alloy undergoes the reverse martensitic transformation from the tetragonal L1₀-type structure with the lattice parameter a_t=0.3853 nm and c_t=0.3299 nm into the B2-type cubic structure with the lattice parameter a_c=0.2924 nm at A_s=383 K. At 408 K (>A_s), we directly observed the field-induced reverse martensitic transformation.