The inverse magnetocaloric effect associated with the martensitic transition in the Ni45.4Mn41.5In13.1 Heusler alloy is reported. A large positive magnetic entropy change of 8J∕kgK under a low magnetic field of 10kOe is found near the martensitic transition temperature. This change originates from the first-order transition from a low-temperature weak-magnetic martensitic phase to a high-temperature ferromagnetic austenitic phase. The large low-field magnetic entropy change indicates a great potential of Ni–Mn–In alloys as working materials for magnetic refrigeration in a wide temperature range.

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The low-field magnetic entropy changes in Ni50−xMn39+xSn11 alloys (x=5, 6, and 7) were investigated. The martensitic transition shifts to lower temperature with the increase of Mn concentration. Under an applied magnetic field of 10kOe, the magnetic entropy changes are 6.8, 10.1, and 10.4J∕kgK, for x=5, 6, and 7, respectively. The large entropy change in Ni50−xMn39+xSn11 can be attributed to the sharp magnetization change associated with the martensitic transition from a ferromagnetic parent phase to a weak-magnetic martensitic phase. The large low-field magnetic entropy change and low cost suggest Ni50−xMn39+xSn11 alloy as the promising magnetic refrigerant.

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The most used method for changing the martensitic transformation temperatures in the ferromagnetic shape memory alloys is tuning the valence election concentration e∕a. In this paper, we report an alternative way, i.e., introducing few interstitial boron atoms in Ni43Mn46Sn11 alloy. The experimental results show that the martensitic transformation temperatures increase with the increasing boron content remarkably and large magnetic entropy changes can be obtained in these alloys. A possible origin of the enhanced martensitic transformation temperatures and large magnetic entropy changes is discussed in this paper.