Magnetodielectric effect in a metamaterial consisting of xerogel with embedded epsilon-Fe2O3 iron oxide nanoparticles

The ε-Fe₂O₃ iron oxide is a fairly rare polymorphic modification, which only exists in the form of nanoparticles embedded, as a rule, into a silica gel matrix. This magnetically ordered iron oxide, which exhibits a significant room-temperature coercivity, is a ferroelectric; therefore, the magnetoelectric and magnetodielectric properties of this material evoke keen interest. In this work, we investigate the magnetodielectric (MD) effect in a metamaterial consisting of xerogel SiO₂ with embedded ε-Fe₂O₃ nanoparticles 9 nm in size on average in a concentration of 20 mass.%. This bulk material exhibits the MD effect in a wide temperature range. The temperature behavior of the permittivity is related to the magnetic state of the ε-Fe₂O₃ oxide, which undergoes the magnetic transition from the magnetically hard to magnetically soft phase in the temperature range of 80–150 K, indicating the interplay of the ε-Fe₂O₃ magnetic and charge subsystems.