Field-induced continuous rotation of the polarization in multiferroic Mn _0.95Co _0.05WO ₄

We report the observation of a continuous rotation of the polarization in Mn _0.95Co _0.05WO ₄ under magnetic field. At zero field, this compound shows a transition into the spiral magnetic and ferroelectric phase at 12.2 K, which is the ground state, with the polarization oriented along the b-axis. Increasing b-axis magnetic fields rotate the ferroelectric polarization continuously toward the a-axis, indicating a rotation of the spin spiral plane. This rotation extends over a large field and temperature range. At a constant magnetic field of 3 T, the polarization also rotates from the a-axis at the ferroelectric transition toward the b-axis upon decreasing temperature.