Impact of Anisotropic Exchange on M-H Loops: Application to ECC Media

TL;DR

This paper investigates how anisotropic exchange interactions influence magnetic hysteresis loops in Co-based media, improving model fit to experimental data and discussing measurement methods for exchange parameters.

Contribution

It introduces a modified exchange interaction model reflecting hexagonal symmetry and demonstrates its impact on magnetic properties and data fitting.

Findings

Jz increases coercivity and loop slope

Enhanced model agreement with experimental in-plane loops

Thermal effects analyzed through temperature-dependent simulations

Abstract

Micromagnetic simulation results on Co-based recording media are presented which examine the impact of a modified near-neighbor exchange interaction between grains of the form Jz(MizMjz), reflecting the hexagonal crystal symmetry. Both out-of-plane and in-plane M-H loops are calculated, with an emphasis on a model fit to data reported by Wang et al. [IEEE Trans. Magn. vol. 43, 682 (2007)] on exchange coupled composite perpendicular media. The principle effect of Jz is to increase the coercivity and slope of both hard and soft layers. Improved agreement with experimental data for the in-plane loops is achieved by assuming a substantial value for Jz. Possibilities for measurement of Jz through spin-wave excitations are discussed. Thermal fluctuation effects are also examined through simulations of the magnetization vs temperature.