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In the present work, polycrystalline Ni50Mn36Sn14-xInx (x = 0, 1, 2 and 3) Heusler alloys were prepared. The influence of In substitution for Sn on the crystal structure, martensitic transition (MT) and magnetic properties have been investigated for these alloys. Structural analysis indicate that the samples possess L21 structure at room temperature. With increasing In content, the martensitic transition shifts to a higher temperature, while the Curie temperature of austenite phase moves to a lower temperature. The maximum entropy change ( Δ SM) max near the martensitic transition is found to be 8.4 J/kgK, 9.8 J/kgK, 10.1 J/kgK and 19.2 J/kgK for x = 0, 1, 2 and 3 respectively, for a field change of 50 kOe. The entropy change around the Curie temperature of the austenite phase is found to be – 2.9 J/kgK, −1.8 J/kgK, −4.1 J/kgK and −3.9 J/kgK respectively for x = 0, 1, 2 and 3 alloys, for a field change of 50 kOe. The effective RCP values are 80 J/kg, 15.6 J/kg, 65.8 J/kg and 69.4 J/kg for x = 0, 1, 2 and 3 alloys respectively, near the first order transition region. The RCP values are higher around the second order transition region due to the broad nature of Δ SM curves. The corresponding values are 114 J/kg, 92 J/kg, 121 J/kg and 132 J/kg for x = 0, 1, 2 and 3 alloys, respectively. Moreover, the critical behavior of Ni50Mn36Sn14-xInx (x = 1, 2 and 3) Heusler alloys around the ferromagnetic-paramagnetic transition region of austenite phase is studied from the field dependence of magnetic entropy change. The critical exponent values are close to the theoretical prediction of mean field model with a slight deviation.

In the present investigation, the effect of iron addition on the structural, magnetic and magnetocaloric properties of Gd5Si1.7Ge2.3-xFex alloys with x = 0–0.4 has been carried out. Structural analysis reveal that Gd5Si1.7Ge2.3-xFex compounds crystallize in a combination of monoclinic and orthorhombic structures at room temperature. With increase in Fe substitution up to x ≤ 0.3, the compounds stabilize in orthorhombic structure with Pbnm space group. First-order and second-order transitions are observed for low Fe concentrations. For x = 0.4, only a second-order transition is evident which is due to the stabilization of the orthorhombic structure. At lower fields, the presence of short-range ferromagnetic correlations indicate competing intra-layer and inter-layer magnetic interactions. The Curie temperature increases from 243 K to 287 K with increase in Fe concentration. The entropy change (-ΔSM) is found to be 10.1 J/kg K at 247 K, 11.3 J/kg K at 253 K, 7.9 J/kg K at 273 K and 7 J/kg K at 287 K for x = 0.1, 0.2, 0.3 and 0.4 respectively, for a field change of 50 kOe. Universal curve analysis corroborates the transition from first-order to second-order as evidenced by magnetization measurements. Tuning the transition temperature to near room temperature through the proper substitution of transition elements paves an interesting route towards the development of materials for room temperature refrigeration applications.