MAGNETIC-BEHAVIOR AND MAGNETOSTRICTION OF TBXY1-XMN2 INTERMETALLICS

The spontaneous magnetic behaviour and the stability of the magnetic m oment on the Mn atoms versus temperature, with concentration, and unde r applied magnetic field and pressure in the series TbxY1-xMn2 have be en investigated by means of magnetostriction up to 14 T, AC susceptibi lity under pressure up to 7 kbar and linear thermal expansion measurem ents. Large volume anomalies were observed in all compounds of the ser ies at T-N, the temperature at which the Mn magnetic moments become lo cal. T-N remains almost constant for x greater than or equal to 0.2. B elow T-N the magnetic structure of Tb-rich compounds is unstable under applied magnetic field and the Mn magnetic moments can be reverted to itineracy. The obtained results can be explained on the assumption th at the transition is non-homogeneous and consequently a small part of the sample does not transform, remaining without Mn local magnetic mom ents below T-N. This region grows either under applied field or under applied pressure and it can occupy the whole sample. From these result s a magnetic phase diagram of this series is proposed.