Magnetocaloric effect in GdRu2Ge2

We have studied the magnetocaloric effect (MCE) in GdRu2Ge2 by means of measurements of temperature and field dependence of the specific heat and the magnetization. Two anomalies were observed at T-1=29 K and T-2=32 K in the zero-field specific-heat curve. Magnetization measurements showed that the magnetic moments of the Gd ions order antiferromagnetically below T-2 and follow the Curie-Weiss Law above T-2. The magnetic measurements also showed that there exists a field-induced antiferromagnetic to ferromagnetic transition below T-1. The magnetocaloric properties estimated from the magnetization measurements by means of the thermodynamic Maxwell relation are in good agreement with those obtained from the specific-heat measurements. The largest observed adiabatic temperature change, DeltaT(ad), is approximately 10 K for a field change from 0 to 15 T. The considerably large magnetic entropy change is due to the field-induced magnetic phase transition, which is magnetically reversible. (C) 2002 American Institute of Physics.