The different magnetic behaviors of LaCoO3 films grown on LaAlO3 and SrTiO3 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 degrees, consistent with the behavior of bulk and nanoparticles forms of LaCoO3. A LaAlO3 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 SrTiO3 substrates, leading to a significant net moment.
@article{arxiv.2108.07965,
title = {Geometric influence on the net magnetic moment in LaCoO$_3$ thin films},
author = {T. Joshi and D. P. Belanger and Y. T. Tan and W. Wen and D. Lederman},
journal= {arXiv preprint arXiv:2108.07965},
year = {2021}
}