The influence of gadolinium on magnetism and magnetocaloric properties of HoCo2 alloy

A series of Ho1−xGdxCo2 (x = 0, 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, 1) samples were prepared by arc-melting method. The crystal structure, magnetic and magnetocaloric effect were investigated by X-ray powder diffraction and magnetization measurements. Then the magnetic phase transition was analyzed in term of Landau theory. The experimental results indicate that the ordering temperature TC increases from 81 to 402 K with increasing Gd substitution so that TC of the alloy is near room temperature (300 K) when x = 0.6. This Curie temperature increase is accompanied by a reduction of entropy change −ΔS. For an external magnetic field change from 0 to 5 T, −ΔS at TC is 11, 4.65 and 3 J/(kg K) for x = 0.1, 0.3 and 0.6, respectively. The origin and the evolution of magnetocaloric effect in Ho1−xGdxCo2 compounds are discussed.