Quantification of L1(0) phase volume fraction in annealed Fe/Pt (n) multilayer films

The heat treatment of [Fe/Pt](n) multilayer films is a promising approach to form the L1(0) FePt phase at a reduced temperature, which is of interest for applications as high-density magnetic recording media and high-energy permanent magnets. The volume fraction of the L1(0) FePt phase in the annealed films strongly influences their magnetic properties. This paper introduces a novel method based on hollow cone dark field transmission electron microscopy imaging to quantify the L1(0) FePt phase volume fraction. This method is used to characterize two sets of [Fe/Pt](n) multilayer films with varying deposition temperature and periodicity. It was found that both the deposition temperature and bilayer periodicity are significant to the structure and magnetic properties of annealed films and to the extent to which the L1(0) phase is formed. A correlation between L1(0) phase volume fraction, grain size, and magnetic properties was also observed