Nanostabilization of tetragonal distorted FeCo variants in ultra-thin FeCo/TiN multilayer films

Composites of ultra-thin nanolayers of FeCo/TiN with individual layer thickness of a few unit cells offer stability at elevated temperatures and exhibit defined magnetic properties which can be tuned by variying the layers thickness making them interesting candiates as components for magnetoelectric (ME) sensors. Initial studies describing the nanostructure of such thin films, however, left uncertainty about their exact crystal structure. With aberration-corrected microscopes the characterization of the local structure down to the atomic scale is possible to address the real structure with high precision. Here, by means of atomic resolution TEM imaging together with X-ray diffraction analysis, we were able to describe the nanostructure to be composed of individual layers of FeCo and TiN forming a superlattice with a defined cube-on-cube orientation relationship. The simulation of electron diffraction pattern featuring superlattice reflections on basis of structural modeling together with geometric phase analysis verified a defined orientation relationship resolving in the nanostabilization of a tetragonal distorted FeCo unit cell with c/a