Electronic ground-state hysteresis under magnetic field in GdMn2O5

In this paper, we investigate the physical properties of the type-II multiferroic ${\mathrm{GdMn}}_{2}{\mathrm{O}}_{5}$ material by means of neutron scattering, electric polarization, and magnetization measurements. A complex (T,H) phase diagram shows up, with especially a field-induced magnetic transition around 11 T at low temperature. The high-field phase is accompanied by an additional electric polarization along both the $a$ and $b$ directions, as authorized by symmetry, but never observed experimentally up to now. While the magnetic properties recover their initial states after driving the field back to zero, the polarization along $a$ shows a significant increase. This behavior is observed for all directions of the magnetic field. It constitutes a novel and striking manifestation of the magnetoelectric coupling, resulting in the establishment of a new ground state at zero magnetic field.