Lattice relaxation and its impact on magnetic properties of FePt thin film

Abstract

The investigation on the lattice relaxation of FePt/TiN heteroepitaxial film was conducted by means of the thickness-dependent evolution of microstructure and magnetic properties. The critical thickness of FePt epitaxial growth on TiN was determined to be around 10 nm based on the lattice constant simulation according to equilibrium theory, which was consistent with the experimental value obtained from cross-sectional transmission electron microscope (TEM) measurements. Using high-resolution TEM images, the lattice relaxation mechanism of the FePt layer was clearly explained via the formation of edge dislocations at the critical thickness and the ensuing tilt of {1 1 1} lattice planes towards the film normal direction. It is found that the lattice relaxation caused the misorientation of the easy axes, and therefore in-plane magnetization increased and perpendicular anisotropy deteriorated with FePt thickness increasing from 10 to 40 nm. © 2013 IOP Publishing Ltd.