Geometric influence on the net magnetic moment in LaCoO$_3$ thin films

Abstract

The different magnetic behaviors of LaCoO 3 films grown on LaAlO 3 and SrTiO 3 are related to the Co-O-Co bond angles and the constraints imposed on the Co-O bond lengths by the substrate geometries. Long-range magnetic order occurs below T ≈ 90 K when the Co-O-Co bond angle is greater than 163 • , consistent with the behavior of bulk and nanoparticles forms of LaCoO 3 . A LaAlO 3 substrate prevents magnetic long-range order at low temperatures near the film substrate interface and collinear antiferromagnetic sublattices away from the interface. At low temperatures, the antiferromagnetically ordered sublattices are non-collinear in films grown on SrTiO 3 substrates, leading to a significant net moment.