Tuning the ferroelectric state in multiferroic TbMnO₃ single crystal by a trapped-charge-induced internal electric field

The pyroelectric current effects in multiferroic TbMnO₃ single crystal are reinvestigated in a wide temperature range. We report a pyroelectric current peak occurring around T = 107 K, which is much higher than the magnetic phase transition temperatures, after poling the sample from T ≥ 60 K to low temperatures, and we attribute it to the thermal release of trapped-charges in TbMnO₃. We also show that the trapped-charges form a strong internal electric field that remarkably controls the ferroelectric polarization state induced by the cycloidal Mn³⁺ spins at lower temperature.