Low-temperature study of magnetic ordering in gadolinium orthophosphate

The zero-field heat capacity shows an antiferromagnetic ordering of Gd³⁺ in gadolinium orthophosphate at 0.8 K. The application of the external magnetic field leads to the splitting of the Gd³⁺ ground-state multiplet. The antiferromagnetic ordering becomes gradually suppressed with increasing field, and the loss of the long-range magnetic ordering with a threshold field between 0.2 and 0.5 T is indicated by heat-capacity data. Estimated entropy of the anomaly due to magnetic ordering or the Schottky-type anomaly (above 0.5 T) is close to Rln8 as expected for Gd³⁺ ground-state multiplet. Magnetization measurements above 2 K corroborate this magnetic behaviour.