Anisotropic Exchange Spin Model to Investigate the Curie Temperature Dispersion of Finite-Size L10-FePt Magnetic Nanoparticles

TL;DR

This paper presents an anisotropic spin model for L10-FePt nanoparticles that accurately predicts Curie temperature dispersion due to size effects, crucial for improving heat-assisted magnetic recording technology.

Contribution

The study introduces an atomistic LLG model incorporating exchange anisotropy, providing a more accurate prediction of Tc dispersion influenced by particle size in magnetic nanoparticles.

Findings

Tc dispersion can be accurately modeled with anisotropic exchange effects.

Approximately 70% of Tc dispersion is due to particle size variations.

Anisotropic models outperform isotropic ones in predicting finite-size effects.

Abstract

We developed an anisotropic spin model that accounts for magnetic anisotropy and evaluated the Curie temperature (Tc) dispersion due to finite size effects in L10-FePt nanoparticles. In heat-assisted magnetic recording (HAMR) media, a next-generation magnetic recording technology, high-density recording is achieved by locally heating L10-FePt nanoparticles near their Tc and rapidly cooling them. However, variations in Tc caused by differences in particle size and shape can compromise recording stability and areal density capacity, making the control of Tc dispersion critical. In this study, we constructed atomistic LLG models to explicitly incorporate the spin exchange anisotropy of L10-FePt, based on parameters determined by first-principles calculations. Using this model, we evaluated the impact of particle size on Tc dispersion. As a result, (1) the Tc dispersion critical to the performance of HAMR can be reproduced, whereas it was previously underestimated by isotropic models and (2) approximately 70% of the experimentally observed Tc dispersion can be attributed to particle size effects. This research highlights the role of exchange anisotropy in amplifying finite-size effects and underscores the importance of size control in HAMR media.