Structure, magnetic properties, and magnetocaloric effect of polycrystalline Ho3M (M = Rh, Ru) alloys

The structure, magnetic properties, and magnetocaloric effect (MCE) of polycrystalline Ho3M (M = Rh, Ru) compounds have been investigated by X-ray diffraction and magnetization measurements. The Ho3Rh sample contains two phases Ho3Rh and Ho7Rh3. Two successive magnetic transitions near 34 and 22 K from the Ho3Rh and Ho7Rh3 phases, respectively, are observed. The maximum magnetic entropy change (-ΔS M) and refrigerant capacity (RC) of the as-cast Ho3Rh alloy are 10.0 J/kg K and 320 J/kg, respectively, for the magnetic field change of 50 kOe. For the Ho3Ru sample, two phases, Ho3Ru, Ho5Ru2, and trace of Ho2O3, are present. Only one Neel transition temperature around 14 K was observed in this multiple-phase sample. The maximal −ΔS M value is 5.1 J/kg K around TN and the value of RC is estimated to be 145 J/kg for ΔH = 50 kOe, which is less than that of the Ho3Rh sample due to the dominant antiferromagnetic interaction. The excellent magnetocaloric performance suggests the potential applicability of Ho3Rh for magnetic refrigeration at low temperatures.