Ferroelectric Polarization Reversal In Multiferroic Mnwo4 Via A Rotating Magnetic Field Up To 52 T

A long-standing issue in multiferroic MnWO4 is the electric polarization reversal when magnetic field is applied along the magnetic easy axis (H parallel to u). In this work, we performed comprehensive ferroelectric polarization measurements on MnWO4 in fields up to 52 T and with rotating field direction in the ac plane. When the field is rotated from H parallel to c to H parallel to u, the induced high-field phase (-P parallel to b) favors a sign reversal relative to the low-field +P parallel to 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 parallel to a causes an abrupt reversal of the high-field phase from -P parallel to b to +P parallel to 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.