Polaron Hopping Induced Giant Room‐Temperature Magnetodielectric Effect in Disordered Rutile NiNb2O6

Abstract

AbstractA majority of the existing magnetodielectric (MD) effects based on spin‐lattice coupling or magnetic transitions are either too weak or far below room temperature, which challenges the potential applications of MD materials. Here, a giant room‐temperature MD coefficient of −62% at 1 Tesla (T) in disordered rutile NiNb2O6 (r‐NiNb2O6) ceramic in terms of the spin‐dependent polaron hopping is demonstrated. The r‐NiNb2O6 exhibits a near‐room‐temperature dielectric relaxation, which is ascribed to the polaron‐hopping‐induced grain polarization. This dielectric relaxation process, strikingly, can be controlled by the external magnetic field (H = 1 T) at 220 K< T< 310 K, achieving a giant MD coefficient of −62% (at 10k Hz) at 298 K. Further systematic investigations on the magnetic, electrical, and magnetoelectric coupling properties attribute the MD effect in r‐NiNb2O6 to a pure response of the spin‐dependent polaron hopping to applied magnetic field. This clearly reveals that the MD effect is subject to a competition among the polaron hopping activation, spin‐lattice coupling, and spin thermal fluctuation.