Computer simulation of coercive force and thermal viscosity in perpendicular recording media

Abstract

The micromagnetic simulations for perpendicular recording media with incoherent magnetization rotation was performed by dividing a grain into subgrains in the direction of film thickness. When intra-grain exchange coupling was smaller, incoherent magnetization rotation occurred, leading to stronger thermal fluctuation effect and lower coercive force . It was found that the critical thickness exists, beyond which the incoherent magnetization rotation occurs.is approximately proportional to 2 5 ( ) 1 2 , where is the intra-grain exchange stiffness constant and is the uniaxial perpendicular anisotropy energy. In the incoherent magnetization rotation, the decreasing rate of by logarithmic time (in thermal viscosity slopes) was larger than that for coherent rotation. The calculations were in good agreement with the experimental coercive forces and thermal viscosity slopes.

Recording media research for future hard disk drives

“…In the case of media with thicker layers, the reversal of the recording media layer could be different from SW type rotation. The RL could be thought to undergo incoherent rotation, where a number of sublayers each of which exhibits intergranular exchange coupling and interacts with the other through interlayer exchange coupling undergo different time evolution of the magnetization reversal [84].…”

Study of attempt frequency in Sharrock's formula for perpendicular recording hard disk media

“…The elapse time t for the temperature T o was transferred by using the relation of obtained from two Arrhenius-Neel equations [7,8], where f o was determined with changing K b , H cro , and C in order that all points of calculated H cr vs. t satisfy Eq. (1) simultaneously [2].…”