Er-driven magnetic tunability in FePt thin films investigated via high-throughput experiments and microstructure analysis for future HAMR media

Abstract

This study undertakes comprehensive experimental validations based on theoretical predictions of the impact of Er and Tm doping on the magnetic properties of FePt thin films. Initial theoretical investigations indicate that doping with rare earth elements may result in promising alterations to the magnetic properties of the FePt thin films, with Er doping in particular offering a promising avenue for further study. Experimental synthesis via a combinatorial high-throughput sputtering system, which enables precise control over the composition of FePt thin films, achieves the desired magnetic properties. Small quantities of dopants, specifically 0.35 at. % Er, substantially enhance the key magnetic properties of saturation magnetization (μ0Ms), anisotropy constant (Ku) at room temperature, and the Curie temperature (TC). Precise microstructural observations of a sample show that Er segregates at grain boundaries, voids, and the substrate/FePt interface, where Er preferentially replaces Fe sites. In other regions of the FePt grains, Er is not solid-soluble, and pure FePt and FePtEr form a composite material in the order of tens of nm. The incorporation of Er also influences the damping constant α. The findings of this study substantiate the intrinsic characteristics of Er-doped films, particularly the enhanced μ0Ms, Ku, and TC attainable with nominal dopant concentrations, and facilitate the realization of ultimate magnetic recording densities anticipated for future data storage technologies.