NEUTRON SCATTERING STUDY OF MAGNETIC ORDER IN A Tb0.5Dy0.5 SINGLE CRYSTAL

Neutron diffraction measurements have been made on Tb0.5Dy0.5 and show initial ordering into a spiral antiferromagnetic phase (with decreasing temperature) and then into a ferromagnetic phase. The inter-layer turn angle changed from 35° to 23° as the temperature moved from the Néel to the Curie temperature. In addition, a magnetostriction-related expansion of the c-axis of about 0.4 % was observed over the same temperature range. The periodic moment state persisted somewhat into the nominal ferromagnetic regime and was accompanied by a slight increase in the turn angle (~ 2°)