Small polaron migration associated multiple dielectric responses of multiferroic DyMnO3 polycrystal in low temperature region

Utilizing temperature dependent dielectric/impedance spectroscopy, multi-dielectric responses involving two dielectric relaxations (DRs) and two magnetic-order-associated dielectric anomalies were observed in polycrystalline DyMnO3. It is elucidated that both DRs’ dynamics, established in terms of equivalent circuit model and small polaron (SP) theories, are closely linked with localized SP migration features. Namely, low-temperature relaxation process can be attributed to short range polaronic variable-range-hopping induced dipolar-type relaxation in grains, whereas the higher-temperature one is due to Maxwell-Wagner relaxation at grain/grain boundary interfaces, which are governed by SP nearest-neighbor-hopping conduction. Additionally, magnetic-orders-associated dielectric anomalies may be assigned to strong spin-lattice couplings by magnetoelasticity-aroused lattice deformation.