Large magnetodielectric effect in nanocrystalline double perovskite Y₂FeCrO₆

Abstract

Double perovskite Y₂FeCrO₆ nanoparticles of diameter 40–60 nm have been prepared by a molten salt synthesis procedure. These exhibit ferromagnetic and relaxor-type ferroelectric transition. The presence of both Fe²⁺ and Cr²⁺ species is confirmed by XPS analysis. The magnetic properties have been explained on the basis of superexchange interaction between Fe²⁺/Fe³⁺ and Cr²⁺/Cr³⁺ and also Kanamori–Goodenough coupling between Fe³⁺/Cr³⁺ species. The relaxor-type behaviour is ascribed to dielectric loss arising due to small polaron hopping conduction between Fe²⁺/Fe³⁺ and Cr²⁺/Cr³⁺ pairs, respectively. A large magnetodielectric coefficient (~25%) at room temperature is caused by a ~30% negative magnetoresistance for a magnetic field of 1.7 T. This has been explained by a model in which spin-polarized electrons hopping through the antiphase boundary contribute higher electrical conductivity to the system when a magnetic field is applied to it.