Suppression and recovery of the ferroelectric phase in multiferroic MnW O4

We report the discovery of a complete suppression of ferroelectricity in MnW O4 by 10% iron substitution and its restoration in external magnetic fields. The spontaneous polarization in Mn0.9 Fe0.1 W O4 arises below 12 K in external fields above 4 T. The magnetic and/or ferroelectric phase diagram is constructed from the anomalies of the dielectric constant, polarization, magnetization, and heat capacity. The observations are qualitatively described by a mean-field model with competing interactions and strong anisotropy. We propose that the magnetic field induces a noncollinear inversion symmetry breaking magnetic structure in Mn0.9 Fe0.1 W O4.