Skip to Main Content
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 a stronger thermal fluctuation effect and lower coercive force Hc. It was found that the critical thickness δc exists, beyond which the incoherent magnetization rotation occurs. δc is approximately proportional to 2.5*(A/Ku)12/, where A is the intra-grain exchange stiffness constant and Ku is the uniaxial perpendicular anisotropy energy. In the incoherent magnetization rotation, the decreasing rate of Hc 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.