Ferroelectric polarization reversal in multiferroic MnWO4 via a rotating magnetic field up to 52 T

Abstract

A long-standing issue in multiferroic ${\mathrm{MnWO}}_{4}$ is the electric polarization reversal when magnetic field is applied along the magnetic easy axis $(H||u)$. In this work, we performed comprehensive ferroelectric polarization measurements on ${\mathrm{MnWO}}_{4}$ in fields up to 52 T and with rotating field direction in the $ac$ plane. When the field is rotated from $H||c$ to $H||u$, the induced high-field phase $(\ensuremath{-}P||b)$ favors a sign reversal relative to the low-field $+P||b$ phase, which is attributed to the vector spin chirality changing from one side of the spin connecting vector to the other. Particularly, further slight deviation of the field from the magnetic easy axis towards $H||a$ causes an abrupt reversal of the high-field phase from $\ensuremath{-}P||b$ to $+P||b$. We assume that this unusual angular dependence of polarization behavior can be understood by magnetic control of the helicity of the chiral plane with opposite conical spin structures. In addition, we also propose electric-field control of the chiral plane close to the ferroelectric phase transition at high fields. This study results in an overall understanding of this important multiferroic material and sheds light on field-induced polarization switching in related compounds.