Phase diagram and dynamics in Er1−xYxMnO3

Strong coupling between the ferroelectric and magnetic order has been previously observed in hexagonal HoMnO3 at a spin reorientation transition between a P6′3cm′ and a P6′3c′m magnetic phases. Understanding the transition between these phases may help illuminate the mechanism of multiferroic coupling in hexagonal R MnO3. In order to study this transition, single-crystal samples of the hexagonal multiferroic Er1−x Yx MnO3 were grown at different compositions. YMnO3 orders in a P6′3cm′ phase, whereas ErMnO3 orders in a P6′3c′m phase. Er1−x Yx MnO3 transitions completely from the P6′3cm′ to the P6′3c′m phase over a very narrow composition range on the Y-rich side of the phase diagram, and the phase boundary exhibits reentrant behavior. Inelastic neutron scattering measurements were performed on these samples, quasielastic scattering similar to that found in YMnO3 was observed. In the P6′3cm′ phase, this quasielastic scattering is centered at Bragg positions which correspond to the P6′3c′m and vice versa. Th...