MAGNETIC-PROPERTIES OF GD-Y ALLOYS - REGULARITIES AND ANOMALIES

The Gd-Y system was investigated in the 0-67 at. % Y concentration range between 4.2 and 350 K, in external fields up to 1 T. The effective paramagnetic moment on Gd atoms was found to be concentration dependent, with a maximum of 9.13 mu(B) at 40.1 at. % Y. Ordered moments on Gd atoms at 5 K showed similar behavior. The observed behavior is consistent with the assumption that Y changed the anisotropy of the crystal field acting on the Gd atoms, resulting in increased total angular momentum. Magnetization data were analyzed to give the thermodynamic transition temperature and the zero-field specific-heat anomaly at the transition. Simultaneously, the change in magnetic entropy for 1 T field was calculated. The magnetic entropy change was found to be nearly concentration independent in the concentration range of increasing Gd atomic magnetic moment. For higher Y contents, the magnetic entropy change sharply decreases. The calculated specific-heat anomaly likewise decreases above 10 at. % Y, and cannot be evaluated for alloys with prevailing helimagnetic structure. The results are in good qualitative agreement with the magnetic phase diagram, obtained via neutron diffraction, although present magnetic measurements provide more details on the critical fields.