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In the present work, polycrystalline Ni45Co5−xPdxMn37In13 (x = 0, 0.5, 1, and 3) Heusler alloys were prepared. The influences of Pd substitution for Co on crystal structure, martensitic transformation (MT), and magnetic properties have been carefully investigated for these quinary alloys. The structure measurement indicates that every sample possesses L10 martensitic structure at room temperature. With increasing of Pd content, it is found that the MT region shifts towards higher temperature, but the Curie transition region of austenitic state moves to lower temperature. Owing to the fact that the MT gradually approaches Curie point, the magnetization of austenitic phase is significantly decreased, while the one of martensitic phase almost remains unchanged. In addition, the functional properties associated with the field-induced reverse MT have been also studied in Ni45Co5−xPdxMn37In13 (x = 0, 0.5, and 1) alloys. In comparison to quaternary parent alloy, both of enhanced magnetostrain (0.3%) and isothermal entropy change (25 J/kg K) are observed in quinary Ni45Co4.5Pd0.5Mn37In13 alloy under an applied magnetic field up to 3 T. The implication of such results has been discussed in detail.

This paper presents the strain behavior associated with martensitic transformation for polycrystalline Ni46Co4Mn39Sn11. The unique reproducible magnetostrain in this alloy has been realized within a magnetic field change of 3 T, and its maximum value achieves about 0.012% at 225 K, which is almost ten times higher than that in Ni-Mn-Sn ternary alloy. Such a reproducible phenomenon could be attributed to the occurrence of the reversible transformation between multi-variant martensite and austenite under an applied isothermal magnetic field.

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