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

TL;DR

This paper investigates how to optimize the microstructure of high-aspect-ratio L1_0-FePt grains in granular thin films for heat-assisted magnetic recording, focusing on temperature grading and grain boundary control.

Contribution

It introduces a method using a stable FePt-BN nucleation layer and temperature grading to produce well-isolated, high-aspect-ratio FePt grains with controlled microstructure.

Findings

Achieved FePt grains over 11 nm in height and less than 7 nm in diameter.

Demonstrated the importance of temperature and SiOx concentration grading.

Provided TEM microstructure analysis under various sputtering conditions.

Abstract

A systematic investigation has been performed to optimize the microstructure of $\mathrm{L1_0-FePt-SiO_x}$ 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 $\mathrm{L1_0-FePt}$ 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.