Magnetodielectric study in SiO2-coated Fe3O4 nanoparticle compacts

TL;DR

This study investigates the dielectric and magnetodielectric properties of SiO2-coated Fe3O4 nanoparticles, revealing both extrinsic and intrinsic coupling effects and suggesting potential for low-loss magnetoelectric applications.

Contribution

It provides new insights into the temperature-dependent magnetodielectric behavior and the role of core/shell nanostructures in Fe3O4 nanoparticles.

Findings

High-temperature dielectric changes are frequency-dependent and due to extrinsic effects.

Low-temperature coupling indicates intrinsic magnetodielectric behavior.

Evidence of multiferroic state in Fe3O4 nanoparticles at low temperatures.

Abstract

The dielectric properties of Fe$_{3}$O$_{4}$ magnetic nanoparticles with an insulating coating layer of SiO$_{2}$ were investigated. At high temperatures, the changes of the dielectric constant and loss induced by the magnetic field are opposite in sign and strongly frequency-dependent, which originates from extrinsic magnetodielectric coupling-the Maxwell-Wagner effect combined with magnetoresistance. And the interface defects leads to the obvious hysteresis phenomena observed in the measurements. On the other hand, the strong coupling of dielectric and magnetic properties at low temperatures contradicts the Maxwell-Wagner model, suggesting the intrinsic magnetodielectric coupling. Our observations are consistent with the recent polarization switching measurements, which confirm the low-temperature multiferroic state existing in highly-lossy Fe$_{3}$O$_{4}$. And the core/shell nanostructure may provide a new route to achieve applicable magnetoelectric materials with low loss.