Change in the character of magnetocaloric effect with Ni substitution in Ho(Co 1− xNi x) 2

In this work, we have studied the magnetocaloric effect (MCE) of Ho(Co 1− x Ni x ) 2 for 0⩽ x⩽0.1. HoCo 2 exhibits a first-order ferrimagnetic to paramagnetic transition at T C=78 K. The substitution of Ni for Co lowers T C of the compound. While the character of the transition and the MCE changes from a first-order type to a second-order type by the Ni substitution, the large MCE at around T C is maintained up to x=0.1. The origin of the large MCE of the compounds is discussed.