Renormalisation of the Néel temperature and magnetocaloric effect in Tb2Agln

The influence of an applied magnetic field on the antiferromagnetic transition temperature of the localised metallic antiferromagnet Tb2AgIn has been studied. Magnetisation measurements show that as the applied field strength increases the transition temperature is shifted to lower temperatures with a B2 dependence as expected on the grounds of symmetry. On the basis of measurements made in static fields of up to 5.5 T, it was estimated that a field of 7.7 T would be sufficient to suppress antiferromagnetic order at T=0 K. This prediction has been confirmed using pulsed high field magnetisation and neutron diffraction measurements in an applied field. The magnetic isotherms have a complex field dependence producing an entropy change ΔS which becomes negative above the Neel temperature ∼58 K. The temperature at which the entropy change passes through zero provides a more precise value for the Neel temperature than can be obtained from Arrott plots. Significant magnetic entropy persists above 58 K and specific heat measurements show that the Rln(13) expected for Tb3+ is only recovered at ∼2.5 TN.