The effect of step-like martensitic transformation on the magnetic entropy change of Ni_40.6Co_8.5Mn_40.9Sn₁₀unidirectional crystal grown with the Bridgman-Stockbarger technique

We report a step-like martensitic transformation and its effect on magnetocaloric properties in Ni_40.6Co_8.5Mn_40.9Sn₁₀unidirectional crystal grown using the Bridgman-Stockbarger technique followed by vacuum annealing at 1173 K for 72 h. This alloy undergoes successive first-order phase transitions which are attributed to the monotonic compositional variation along the crystal growth direction; the latter results in the increase of the full-width at half-maximum of the magnetic entropy change as a function of temperature (δT_FWHM). For a magnetic field change of 2 and 5 T, the maximum magnetic entropy change are 9.7 and 16.0 J kg⁻¹K⁻¹with an extended δT_FWHMof 11 and 23 K, respectively. The average hysteresis loss for a field change of 2 T is 19 J kg⁻¹reducing the refrigerant capacity by 17%.