Large magnetodielectric effect in nanocrystalline double perovskite Y2FeCrO6

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 (similar to 25%) at room temperature is caused by a similar to 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.