Ab Initio Study of the Polarization, Electronic, Magnetic, and Optical Properties of Perovskite SrMO3 (M = Fe, Mn) Crystals and Thin Films Containing Magnetic Ions

The magnetic, electronic, and polarization properties of the SrFeO₃ and SrMnO₃ compounds with a perovskite structure are calculated using the density functional theory in the bulk and thin-film states. A ferroelectric instability is found to be absent in the bulk state, and the polar mode is softened in the thin-film state of SrMnO₃ in the presence of tensile stresses in the substrate. As a result, a polar phase with a polarization of 23 μC/cm² appears, which agrees with experimental data. The study of the magnetic and electronic properties demonstrates the existence of G-type antiferromagnetic ordering in SrMnO₃ and the appearance of a dielectric gap of about 1.5 eV in its thin film. A ferromagnetic phase with metallic conduction in both the bulk and thin-film states is detected in SrFeO₃.