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

The Gd-Y system was investigated in the 0-67 at. % Y concentration ran ge 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 dependen t, 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 consis tent with the assumption that Y changed the anisotropy of the crystal field acting on the Gd atoms, resulting in increased total angular mom entum. Magnetization data were analyzed to give the thermodynamic tran sition temperature and the zero-field specific-heat anomaly at the tra nsition. Simultaneously, the change in magnetic entropy for 1 T field was calculated. The magnetic entropy change was found to be nearly con centration independent in the concentration range of increasing Gd ato mic magnetic moment. For higher Y contents, the magnetic entropy chang e sharply decreases. The calculated specific-heat anomaly likewise dec reases above 10 at. % Y, and cannot be evaluated for alloys with preva iling helimagnetic structure. The results are in good qualitative agre ement with the magnetic phase diagram, obtained via neutron diffractio n, although present magnetic measurements provide more details on the critical fields.