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

A 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.

Automated summary

In disordered rutile NiNb2O6 ceramic, a giant room-temperature magnetodielectric effect is demonstrated due to spin-dependent polaron hopping, which can be controlled by an external magnetic field within a specific temperature range. These findings highlight the competition between polaron hopping activation, spin-lattice coupling, and spin thermal fluctuation in realizing the magnetodielectric effect.