Thermal expansion of the magnetorefrigerant Gd5(Si,Ge)4

We report thermal expansion measurements carried out on a single-crystal of the giant magnetocaloric effect material Gd5(Si0.43Ge0.57)4. At the magneto-structural phase transition at T0∼240 K, large steps in the relative length change ΔL/L along the principle crystallographic axes are observed. The single-step behaviour in ΔL/L indicates that the magnetic and the structural phase transition occur at one and the same temperature. The specific heat was measured in order to determine the latent heat. Using the Clausius–Clapeyron relation, we extract a hydrostatic pressure dependence dT0/dP of 3.2±0.2 K/kbar. The pressure effect is strongly anisotropic as follows from the anisotropy in the linear thermal expansion. Uniaxial pressure along the a-axis enhances T0, while uniaxial pressure in the bc-plane suppresses T0.