TEM-based crystal structure analysis of body-centered tetragonal structure in non-epitaxial FeCo film with added V and N

[Display omitted] •bct-FeCo was formed via non-epitaxial growth.•Tetragonally distorted bct lattice was observed in polycrystalline materials.•The addition of V and N to FeCo stabilized the bct structure. FeCo with a tetragonally distorted, body-centered tetragonal (bct) structure has been grown epitaxially for investigating the basic magnetic properties; however, it is necessary to form the bct-FeCo without epitaxial growth for allowing their use in permanent magnet-based applications. In this study, we investigated the effect of adding V and N to non-epitaxial FeCo films by directly depositing FeCoVN films on an amorphous SiO2 substrate. Crystal structure analysis performed through transmission electron microscopy revealed a bct lattice with an axial ratio of 1.07 at 10 at.% V and 1.5 at.% N. The tetragonal distortion stability was evaluated using first-principles calculations. The results indicated that bct-FeCo was formed via non-epitaxial growth, and the addition of V and N stabilized the bct structure.