Giant magnetocaloric effect in the Gd₅Ge_2.025Si_1.925In_0.05 compound

The magnetocaloric properties of the Gd₅Ge_2.025Si_1.925In_0.05 compound have been studied by x-ray diffraction, magnetic and heat capacity measurements. Powder x-ray diffraction measurement shows that the compound has a dominant phase of monoclinic Gd₅Ge₂Si₂-type structure and a small quantity of Gd₅(Ge,Si)₃-type phase at room temperature. At about 270 K, this compound shows a first order phase transition. The isothermal magnetic entropy change (\Delta S_M) is calculated from the temperature and magnetic field dependences of the magnetization and the temperature dependence of MCE in terms of adiabatic temperature change (\Delta T_ad) is calculated from the isothermal magnetic entropy change and the temperature variation in zero-field heat-capacity data. The maximum \Delta S_M is -13.6 J\cdotkg^-1\cdotK^-1 and maximum \Delta T_ad is 13 K for the magnetic field change of 0--5 T. The Debye temperature (\theta_D) of this compound is 149 K and the value of DOS at the Fermi level is 1.6 states/eV.atom from the low temperature zero-field heat-capacity data. A considerable isothermal magnetic entropy change and adiabatic temperature change under a field change of 0--5 T jointly make the Gd₅Ge_2.025Si_1.925In_0.05 compound an attractive candidate for a magnetic refrigerant.