THE MAGNETIC PHASE-DIAGRAM OF TBXY1-XMN2 INTERMETALLICS UNDER PRESSURE USING NEUTRON-DIFFRACTION

The magnetic phase diagram of the intermetallic compounds TbxY1-xMn2 h as been studied under pressure using neutron diffraction. At ambient p ressure all compounds undergo a first-order magnetic transition as the Mn magnetic moment becomes local, giving rise to a transformed phase, with higher volume. Part of the sample can remain non-transformed and the two phases coexist below the transition temperature. As pressure is applied the relative volume percentages of the transformed phase an d non-transformed phases change as the transformed phase becomes unsta ble under pressure. At high enough pressures only the non-transformed phase is present. Within the non-transformed phase, for x > 0.2 there is a transition to a magnetic structure which is reminiscent of the Dy Mn2-like structure while for x less than or equal to 0.2 the structure remains paramagnetic. In the transformed phase the TbMn2-like magneti c structure develops at high Tb concentrations while at low Tb concent rations two different antiferromagnetic structures are visible, a YMn2 -like structure and a new antiferromagnetic structure unknown up to no w. Across the intermediate-concentration range a magnetic ground state with short-range correlations is present.