The effect of high tensile strain and low dimensionality on the magnetic and electronic properties of $\mathrm{Ca}\mathrm{Mn}{\mathrm{O}}_3$ ultrathin films, epitaxially grown on $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ substrates, are experimentally studied and theoretically analyzed. By means of ab initio calculations, we find that both the high strain produced by the substrate and the presence of the free surface contribute to the stabilization of an in-plane ferromagnetic coupling, giving rise to a nonzero net magnetic moment in the ultrathin films. Coupled with this change in the magnetic order we find an insulator-metal transition triggered by the quantum confinement and the tensile epitaxial strain. Accordingly, our magnetic measurements in 3-nm ultrathin films show a ferromagnetic hysteresis loop, absent in the bulk compound due to its G-type antiferromagnetic structure.

• Received 19 March 2020
• Revised 10 July 2020
• Accepted 4 August 2020

DOI:https://doi.org/10.1103/PhysRevB.102.085432