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Structural and magnetocaloric properties of Nd substituted Gd5-xNdxSi2Ge2 with x = 0.05, 0.1, and 0.2 have been investigated. The composition with x = 0.05 crystallizes in monoclinic Gd5Si2Ge2 structure with P112(1)/a space group and undergoes a first order phase transition with a Curie temperature of 275 K. With increase in Nd content to x = 0.1, the compound is found to stabilize in orthorhombic Gd5Si4 phase with Pnma space group. The compounds with x = 0.1 and 0.2 undergoes a second order magnetic transition at 300K and 293 K, respectively. Temperature variation of maximum entropy change for Gd5-xNdxSi2Ge2 alloys with x = 0.05, 0.1, and 0.2 are 7.9, 3.7, and 3.2 J/kg K, respectively, for a field change of 20 kOe, and 12.8, 7.6, and 7.2 J/kg K, respectively, for 50 kOe. A large relative cooling power of 295, 205, and 188 J/kg are obtained for x = 0.05, 0.1, and 0.2, respectively, fulfilling the required criteria for a potential magnetic refrigerant in the room temperature regime. (C) 2015 AIP Publishing LLC.

Microstructure and magnetocaloric effect were investigated in Gd1-x(Si0.5Ge0.5)(x) alloys with x = 0.38, 0.41, 0.45, 0.47 and 0.50. The phase identification and compositional analysis were carried out by a combination of x-ray powder diffraction, scanning electron microscopy and electron probe microanalysis. The Gd-5(Si,Ge)(4) phase was found to have an orthorhombic Gd5Si4-type structure when the coexisting phase was Gd-rich (Gd5Si3-type) and a monoclinic Gd5Si2Ge2-type structure when the coexisting phase was Gd-depleted (Gd5Ge5-type). The magnetocaloric effect was found to depend on the volume fraction and the Si/Ge ratio of the ferromagnetic 5 : 4 phase in the above series of alloys. A maximum magnetocaloric effect ( Delta S) M of 14.3 J kg(-1) K-1 for a magnetic field change from 0 to 5 T was obtained for the x = 0.45 alloy.