Field-induced continuous rotation of the polarization in multiferroic   Mn$_{0.95}$Co$_{0.05}$WO$_{4}$
  We report the observation a continuous rotation of the polarization in Mn$_{0.95}$Co$_{0.05}$WO$_{4}$ under magnetic field. At zero field, this compound shows a transition into the spiral magnetic and ferroelectric phase at 12.2K, 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 Tesla, the polarization also rotates from the a-axis at the ferroelectric transition toward the b-axis upon decreasing temperature. 
K.-C. Liang, R. P. Chaudhury, Y. Q. Wang, Y. Y. Sun, B. Lorenz, C. W.   Chu
cond-mat.str-el cond-mat.mtrl-sci