Strain-engineered high-temperature ferromagnetic oxygen-substituted NaMnF3 from first principles

Using first-principles calculations, we investigated the magnetic, electronic, and structural properties of oxygen-substituted ${\mathrm{NaMnF}}_{3}$ $({\mathrm{NaMnF}}_{1.5}{\mathrm{O}}_{1.5})$ with in-plane biaxial strain. For simplicity, a structure containing an oxygen octahedron is used to explore the underlying physical mechanism. We found that the oxygen octahedron induces a transition from an insulating antiferromagnet to a high-temperature half-metallic ferromagnet. More importantly, the Curie temperature can be significantly enhanced and even might reach room temperature by applying tensile strain. The changing trends of exchange coupling constants with the increasing biaxial tensile strain can be attributed to the cooperative effects of Jahn-Teller distortion and rotation distortion. It is expected that these findings can enrich the versatility of ${\mathrm{NaMnF}}_{3}$ and make it a promising candidate for spintronic applications.