Investigation Of Fine Structure And Magnetic Property Of Double Perovskite By Transmission Electron Microscopy

Superexchange-based magnetic coupling of the two B-site cations in rock-salt-ordered double perovskite oxides is extremely sensitive to the cation ratio and degree of order.However,as a result of the limited spatial resolution of most magnetic characterization techniques,it is challenging to establish a direct relationship between magnetic properties and structure in these materials,including the effects of elemental segregation and cation disorder.Here,we use electron energy-loss magnetic chiral dichroism together with aberration-corrected electron microscopy and spectroscopy to record magnetic circular dichroism?MCD?spectra at the nm scale,in combination with structural and chemical information at the atomic scale from the very same region.We study nanoscale phases in ordered Sr₂[Fe][Re]O₆,ordered Sr₂[Fe][Fe_1/5Re_4/5]O₆ and disordered Sr[Fe_4/5Re_1/5]O₃ individually,in order to understand the role of cation ratio and order on local magnetic coupling.When compared with ordered Sr₂[Fe][Re]O₆,antiferromagnetic Fe³⁺-O^2--Fe³⁺superexchange interactions arising from an excess of Fe suppress the MCD signal from Fe cations in ordered Sr₂[Fe][Fe_1/5Re_4/5]O₆,while dominant Fe³⁺-O^2--Fe³⁺antiferromagnetic coupling in disordered Sr[Fe_4/5Re_1/5]O₃ leads to a decrease in MCD signal,down to the noise level.Our work demonstrates a protocol that can be used to correlate crystallographic,electronic and magnetic information in materials such as Sr₂Fe_1+xRe_1-xO₆,in order to provide insight into structure-property relationships in double perovskite oxides at the atomic scale.Eventually,we reveal an ordered phase case of perovskite-Sr₃Fe₂ReO₉,which can be acquired by aberration-corrected electron microscopy,its structure of boundaries with ferromagnetic and antiferromagnetic would become an alternative topic we interested.