Direct Measurement of the Magnetocaloric Effect in Gd₅Si₂Ge_1.9Ga_0.1

Doping with some metals (Fe, Cu, Ga, Mn, Al) reduces or removes the strong thermal hysteresis in the giant magnetocaloric alloys Gd₅(Si_xGe_1−x)₄. We present heat capacity and direct measurements of the isothermal entropy change, ΔS_T, and adiabatic temperature increment, ΔT_S, of Gd₅Si₂Ge_1.9Ga_0.1. T_C = 293.6 ± 0.2 K is quite higher than in the non-substituted alloys and similar to the values in the Si rich compounds (i.e. x > 0.5). The results indicate that even this small addition of Ga makes the transition of second-order type, as a usual magnetic transition in the orthorhombic phase. The magnetocaloric parameters are lower than in the non-substituted compound and comparable to those for pure Gd.