Oxygen octahedral coupling and structural reconstruction at the intergrowth interface in bilayered Ca3Mn2O7

Nanoscale intergrowth is a ubiquitous phenomenon in layered manganites, and the interaction with the host material results in structural reconstruction around the interface, which plays an important role in the physical properties, similar to the interface effect happening in oxide heterostructures. In this work, by combining the aberration-corrected scanning transmission electron microscopy and density functional theory calculations, the oxygen octahedral coupling at the interface was directly visualized and quantified at atomic scale, and the role of oxygen octahedral coupling in the microstructure and electronic structure of bilayered Ca3Mn2O7 were studied. The intergrowth induced interfacial phases show different octahedral tilting angles which depend on the form of nanoscale intergrowth, and thus are structurally and electronically different from bulk materials. These findings can well explain the observed mixture of tetragonal and orthorhombic phases in Ca3Mn2O7 at room temperature, and also offers great insights into understanding of peculiar magnetism induced by the presence of intergrowth. Since the tilting angle of these intergrowth induced phases can be controlled by the thickness and density of the intergrowth, the latter could have the potential to be used to tune the physical properties.

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