The authors report the observation of exchange bias in bulk polycrystalline Ni 50 Mn 25+x Sb 25−x Heusler alloys. Shifts in hysteresis loops of up to 248 Oe were observed in the 5 T field cooled samples. The observed exchange bias behavior in Ni 50 Mn 25+x Sb 25−x is attributed to the coexistence of antiferromagnetic and ferromagnetic exchange interactions in the system. Such behavior is an addition to the multifunctional properties of the Ni 50 Mn 25+x Sb 25−x Heusler alloy system.

We present the magnetocaloric properties of the substituted Heusler alloy Ni2Mn1−xCuxGa, which shows a maximum magnetic entropy change of ΔSM≈−64J∕KgK=−532mJ∕cm3K at 308K for a magnetic field change ΔH=5T. The dependence of ΔSM on ΔH is approximately linear and does not reach saturation at 5T. It is demonstrated that the temperature at which ΔSM occurs can be tuned through subtle variations in composition.

The magnetocaloric properties of polycrystalline Ni 50 Mn 50−x In x ͑15ഛ x ഛ 16͒ associated with the second order magnetic transition at the Curie temperature and the first order martensitic transition were studied using magnetization measurements. The refrigeration capacity and magnetic entropy change were found to depend on the In concentration and reach a maximum value of refrigeration capacity of 280 J / kg with a magnetic entropy change of −6.8 J / kg K at 318 K for a magnetic field change of 5 T. These values of the magnetocaloric parameters are comparable to that of the largest values reported near the second order transition of metallic magnets near room temperature.

A study of the magnetocaloric effect ͑MCE͒ in the ferromagnetic Heusler alloys Ni 50 Mn 37+x Sb 13−x ͑x =0,0.5,1͒ has been carried out through magnetization measurements. An inverse magnetocaloric effect was observed in the vicinity of the first order martensitic transition. A maximum positive magnetic entropy change of ⌬S m Ϸ 19 J / kg K at approximately 297 K for a magnetic field change of 5 T was observed. It is demonstrated that the martensitic transformation temperature, and the corresponding ⌬S m , can be tuned through a slight variation in composition.

An experimental study on the exchange bias properties of bulk polycrystalline Ni 50 Mn 50−x Sn x Heusler alloys has been performed. Martensitic transformations have been observed in the alloys for some critical Sn concentrations. The alloys, while in their respective martensitic phases, are found to exhibit exchange bias effect. Shifts in hysteresis loops of up to 225 Oe were observed in the 50 kOe field cooled samples. The observed exchange bias behavior in Ni 50 Mn 50−x Sn x is attributed to the coexistence of antiferromagnetic and ferromagnetic exchange interactions in the system.