Model of advanced recording media : The angular dependence of the coercivity including the effect of exchange interaction

We use a micromagnetic model based on the kinetic Monte-Carlo approach to investigate theoretically the magnetic properties of advanced recording media. The model is employed to examine the impact of the magnetostatic and exchange interaction between grains of realistic perpendicular recording media on the angular-dependent coercivity since the exchange field between grains is an important factor in recording performance. The micromagnetic model allows to take the easy axis distribution and the exchange interaction between grains into account. The results confirm the importance of exchange interaction since the variation of coercivity with angle between the applied field and the orientation of easy axis which is perpendicular to the film plane, (θ) is seen to broaden with decreasing exchange field. We show that a two-stage fitting procedure involving the separate determination of the exchange field and easy axis dispersion provides a useful tool for the characterization of media for perpendicular recording and heat assisted recording. We find excellent agreement between previous experimental results and the simulations including exchange interactions leading to estimate of the exchange coupling and easy axis dispersion.