Control of the ferroelectric properties ofDyMn2O5by magnetic fields

Abstract

Coupling between magnetic and dielectric properties has been attracting renewed interest because of the fundamental as well as technological importance of controlling the electric (magnetic) polarization by an external magnetic (electric) field. Here, we report the phenomenon that an external magnetic field induces and/or modifies ferroelectric states in a magnetic material, $\mathrm{Dy}{\mathrm{Mn}}_{2}{\mathrm{O}}_{5}$. Measurements of the temperature dependence of hysteretic polarization curves, pyroelectric current, specific heat, optical second harmonic generation, and x-ray superlattice peaks have revealed successive phase transitions between 43 and $4\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, accompanying three ferroelectric phases. The zero-field lowest-temperature phase $(<8\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ induced by the Dy-moment ordering is a reentrant paraelectric state, but is turned into a ferroelectric state with increasing magnetic field. The phenomenon is closely related to the metamagnetic transitions of the Dy $f$ moment, indicating that all the ferroelectric phases of this material are strongly tied to the antiferromagnetic Mn spin structure affected by the $f\text{\ensuremath{-}}d$ exchange interaction. The electric phase diagram for $\mathrm{Dy}{\mathrm{Mn}}_{2}{\mathrm{O}}_{5}$ is presented in the plane of temperature and magnetic field.