First order ferromagnetic transition in binary CeIn₂

Measurements of the magnetic, thermal, and transport properties of the CeIn₂ binary alloy are consistent with a paramagnetic-ferromagnetic transition at T_C=22 K. A discontinuity in the magnetic entropy, electrical resistivity and thermal expansion, and a huge anomaly in the specific heat of 113 J/mol K (Δc_mag=103 J/mol K), at the magnetic transition, are observed. In addition, the Arrott plots show negative slope at low fields, the field-cooling and field-warming magnetization present irreversibility, and both the susceptibility and the resistivity evidence a small thermal hysteresis of 0.05 K. Moreover, the values of the entropy change calculated from the magnetization data using the Clausius-Clapeyron equation are in good agreement with those directly obtained from the specific-heat data. The joint analysis of all these results provides evidence for the first order character of this magnetic transition in CeIn₂.