  Using first-principles calculations, we investigated the magnetic,
electronic, and structural properties of oxygen-substituted NaMnF3
(NaMnF1.5O1.5) 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
NaMnF3 and make it a promising candidate for spintronic applications.
