Magnetic properties of NiMn-based Heusler alloys influenced by Fe atoms replacing Mn

The influence of the Mn substitution by Fe atoms on the magnetocaloric and magnetic properties of the martensitic Ni(50)Mn(36)Sn(14) Heusler-type compound has been investigated using magnetization measurements. The insertion of Fe atoms reduces the Mn-Mn AF interactions resulting in (i) a systematic decrease in the martensitic transition temperature, down to its disappearance at 15 at. % of Fe, (ii) an enhancement of the saturation magnetization, and (iii) a monotonic increase in the L2(1)-type phase Curie temperature. The Fe substitution also induces metamagnetic transition from an incipient AF to a noncollinear spin configuration for applied magnetic fields higher than 3 T in the case of 3 and 7 at. % Fe substitutional. The exchange-bias effect is only found in compounds with a well-defined martensitic phase transition (Fe content lower than 10 at. %). The maximum of the inverse magnetic entropy change, for a field variation of 5 T, is about +12 J kg(-1) K(-1) and it is nearly constant for Fe content up to 7 at. %. This observation suggests that the Ni(50)(Mn(1-x)Fe(x))(36)Sn(14) Heusler-type compounds could be used to prepare composites with potential for technological application in magnetic refrigerators.