Influence of Fe addition on the microstructure, magnetic properties and magnetocaloric behavior of Gd5Si1.7Ge2.3

Abstract

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.