Double-loop hysteresis in tetragonal KTa_0.58Nb_0.42O₃ correlated to recoverable reorientations of the asymmetric polar domains

KTa_1-xNb_xO₃ single crystals are typically regarded as normal ferroelectrics. Such crystals are thought to undergo a paraelectric-ferroelectric phase transition from the cubic to the tetragonal phase where generally a single hysteresis loop is expected. Nevertheless, a double-loop hysteresis is clearly observed in the tetragonal phase of KTa_0.58Nb_0.42O₃. Our investigations reveal further that the double loop exhibits good ergodicity during changes in temperature under various applied electric fields. The origin of this unusual double-loop hysteresis in tetragonal KTa_0.58Nb_0.42O₃ is revealed with the recoverable reorientation of the asymmetric polar domains.