Magnetostructural transformation and magnetocaloric effect of Sn-bonded Mn 0.66 Fe 0.34 Ni 0.66 Fe 0.34 Si 0.66 Ge 0.34 composite

Magnetostructural coupling in MnMX (M = Co or Ni, X = Si or Ge) system attracts considerable attention for the accompanied multi-magnetoresponsive effects. However, due to the large stress generated from the structural transformation, the alloys become shattered or powder-like, hindering the further investigation and their applications. The possible solution is to embed the MnMX powders into metal matrix. In this paper, we choose Mn0.66Fe0.34Ni0.66Fe0.34Si0.66Ge0.34 as a representative of MnMX alloy and produce Mn0.66Fe0.34Ni0.66Fe0.34Si0.66Ge0.34/Sn composite bulk by hot pressing. The magnetostructural-coupled composites exhibit an improved rate of the transformation temperature shift by magnetic field and broadened operating temperature range. Additionally, we also propose a simple formula based on the entropy-temperature diagram to calculate the isothermal entropy change, which is consistent with the results obtained by the Maxwell relation.