Comparison of h-BN and graphene layers as grain boundary materials for granular FePt-$\text{L}1_0$ thin films

TL;DR

This study compares h-BN and graphene as grain boundary materials in FePt thin films, finding graphene's potential but highlighting the need for improved deposition techniques to optimize microstructure for heat-assisted magnetic recording.

Contribution

It introduces multilayer graphene as an alternative to h-BN for grain boundary engineering in FePt films, exploring its effects on microstructure and magnetic properties.

Findings

Graphene nanoribbons wrapped around FePt grains with 7.5 nm diameter.

Perpendicular coercivity of 40 kOe achieved.

Graphene's effectiveness limited by amorphous carbon in grain boundaries.

Abstract

Granular $\text{L}1_0$-FePt thin films with small columnar grains are essential for heat-assisted magnetic recording media. While hexagonal boron nitride(h-BN) has proven effective for promoting columnar FePt grains, we explored multilayer graphene as an alternative grain boundary material leveraging its structural similarity to h-BN. The FePt granular thin films with carbon-based grain boundary materials(GBMs) were deposited by cosputtering on Si/SiO2 substrates with substrate bias at 650{\deg}C. The RF bias and high temperature facilitated formation of interlinked graphene nanoribbons wrapping around FePt grains, yielding 7.5 nm diameter, 8 nm height grains with an order parameter of 0.78 and a perpendicular coercivity of 40 kOe. However, the formation of graphene nanoribbons could not effectively promote columnar structures, likely due to co-existing amorphous carbon in grain boundaries. Optimizing deposition to improve graphene grain boundary quality is necessary to realize this 2D material's potential for achieving desirable microstructures for HAMR media.