Direct Measurement of the Magnetocaloric Effect in Gd5Si2Ge1.9Ga0.1.

Doping with some metals (Fe, Cu, Ga, Mn, Al) reduces or removes the strong thermal hysteresis in the giant magnetocaloric alloys Gd-5(SixGe1-x)(4). We present heat capacity and direct measurements of the isothermal entropy change, Delta S-T, and adiabatic temperature increment, Delta T-S, of Gd5Si2Ge1.9Ga0.1. 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.