Stabilisation of tetragonal FeCo structure with high magnetic anisotropy by the addition of V and N elements

The development of magnetic materials with high saturation magnetization (M-s) and uniaxial magnetic anisotropy (K-u) is required for the realisation of high-performance permanent magnets capable of reducing the power consumption of motors and data storage devices. Although FeCo-based materials with the body-centred cubic structure (bcc) exhibit the highest M-s values among various transition metal alloys, their low K-u magnitudes makes them unsuitable for permanent magnets. Recent first-principles calculations and experimental studies revealed that the epitaxial FeCo thin films with the body-centred tetragonal (bct) structure and thicknesses of several nanometres exhibited K-u values of 10(6) J.m(-3) due to epitaxial stress, which required further stabilisation. In this work, the FeCo lattice stabilised via VN addition were characterised by high K-u magnitudes exceeding 10(6) J.m(-3). The obtained bct structure remained stable even for the films with thicknesses of 100 nm deposited on an amorphous substrate, suggesting its possible use in bulk systems.