Understanding the growth of high-aspect-ratio grains in granular L10-FePt thin-film magnetic media

Abstract

A systematic investigation has been performed to optimize the microstructure of $\mathrm{L}{1}_0-\mathrm{FePt}-\mathrm{Si}{\mathrm{O}}_{\mathrm{x}}$ granular thin film as recording media for heat-assisted magnetic recording. The FePt-BN nucleation layer, which is stable even at $700^{\circ }\text{C}$, is used to control the grain sizes and microstructure during high-temperature processing. The study finds that films of high-aspect-ratio FePt grains with well-formed silicon oxide (SiOx) grain boundaries require the grading of the deposition temperature during film growth as well as the grading of the silicon oxide concentration. Well-isolated columnar grains of $\mathrm{L}{1}_0-\mathrm{FePt}$ with an average height greater than 11 nm and diameters less than 7 nm have been achieved. Transmission electron microscopy (TEM) analysis of the microstructures of samples produced under a variety of non-optimal conditions is presented to show how the microstructure of the films depends on each of the sputtering parameters.

17 pages, 7 figures, first published in joint MMM-intermag 2022