Structural and disorder effects on the magnetic behavior of Ce(In1−xNix)2 alloys

We have investigated the evolution of the magnetic and thermal properties on the Ce(In1−xNix)2 (x=0.025 and 0.05) series of alloys. The orthorhombic structure of the CeIn2 alloy changes to hexagonal AlB2-type for the Ni-diluted samples. The dc (ac) magnetic susceptibility and specific heat measurements show a change from first-order ferromagnetism in the CeIn2 alloy (x=0) to second order ferromagnetism upon chemical substitution of Ni, with an abrupt decrease of the transition temperature from 22 K to 6.3 K (x=0.025). The results indicate a preeminent role of the crystallographic type of structure and disorder effects on the magnetic behavior along the series.