Field dependence of the magnetic structure of TbMn2O5

The evolution of the magnetic propagation vector of the magnetically ordered phases of TbMn2O5 has been studied as a function of magnetic field applied parallel to both [010] and [100] axes. The results have been used to construct (H, T) phase diagrams showing the regions of stability of the three distinct phases IC1, C, and IC2 known to exist in zero field. Application of magnetic field along [010] increases the stability range of the commensurate C phase at the expense of the two incommensurate phases IC1 and IC2, whereas applying the field along [100] has the opposite effect. The evolution with field of the magnetic structure of the C phase has been determined from the integrated intensities of sets of magnetic reflections measured with different field values. With the field along [010], there are no significant changes in structure in fields up to 6 T. Applying the field parallel to [100] leads to an apparently continuous increase in the z component of the propagation vector from 0.25 in zero field to approximate to 0.3 in 6 T. This change is accompanied by increasing ferromagnetic polarisation of the Tb sublattices. Polarised neutron measurements made on the fundamental reflections show that there is no significant ferromagnetic polarisation of any the Mn sublattices in fields of up to 6 T. (C) 2014 AIP Publishing LLC.