Abstract
Manganese oxides with spinel structure could exhibit abundant physical effects due to the complex sublattice structure, variable valence states and the intricate roles of manganese cations in magnetic interaction. In this work, NiMn2O4 ceramic with space group of Fd3‾m is synthesized. The low-temperature polarization behavior is investigated accompanied by revealing the multi-stage dielectric relaxation. Moreover, the relaxation mechanism is confirmed through microstructure characterization, multiple-condition pyroelectric measurement and the dielectric tunability properties under electric/magnetic fields. With increasing measuring temperature, different relaxation phenomena are respectively induced by lattice distortion because of the competition among magnetic coupling interactions (below ∼135 K), electron hopping relating to the coexistence of different valence states of manganese ions (∼135–230 K), and the synergistic contribution of oxygen vacancies and domain wall effect (above ∼230 K). These results provide additional evidence for comprehensive understanding the low-temperature polarization in NiMn2O4, guiding the method design for exploring the physical origin within a wide temperature range.
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