The magnetic field dependent phase diagrams of the ferrielectric material ${\mathrm{Ho}}_{1-x}{\mathrm{Y}}_x\mathrm{Mn}{\mathrm{O}}_3$ have been investigated for $x=0$, 0.6, and 0.8 for fields directed along both the ab in-plane and the $c$-axis directions. Dielectric measurements are used to map out the reentrant temperature-magnetic field phase transitions which involve in-plane Mn spin rotations in the antiferromagnetic state below the Néel temperature. We describe this behavior in terms of the interaction of the Ho sublattice spin system with the underlying, robust $\mathrm{Y}\mathrm{Mn}{\mathrm{O}}_3$ antiferromagnetic triangular lattice, where the Ho-Y spin interactions are highly sensitive to concentration and field direction.

• Received 28 July 2006

DOI:https://doi.org/10.1103/PhysRevB.75.014436