The equivalency between hydrostatic pressure and Si doping in the giant magnetocaloric compound Gd$_{5}$(Si$_{x}$Ge$_{1-x})_{4}$ studied by X-Ray Magnetic Circular Dichroism.

The effect of pressure (P$\le $150 kbar) upon the magnetic properties of giant magnetocaloric material Gd$_{5}$(Si$_{x}$Ge$_{1-x})_{4}$ (x=0.125, 0.5) was investigated by x-ray magnetic circular dichroism measurements in a diamond anvil cell. The ferromagnetic Curie temperature, Tc, increases linearly with pressure albeit with different slopes dTc/dP for x=0.125 and 0.5. This pressure dependence of Tc, together with a discontinuity in Tc (P) at $\sim $274K, are also observed in the x-T phase diagram. The equivalency of pressure and Si demonstrates that the magnetic properties in this class of materials are controlled by volume, and not by preferential substitution of Si/Ge at certain lattice sites.