Micromagnetic studies on exchange-coupled composite media

In order to understand the recording characteristics of the media, the magnetic dynamics of a total recording system with a single pole head (SPH) and exchange-coupled composite media with recording layer (RL) and semi-hard layer (SHL) were examined by a 3-D micromagnetic model. Effects of the interlayer exchange coupling (Jex) between the RL and the SHL as well as thickness, anisotropy constant (Ku), intergranular exchange coupling (A*) of the SHL on SNR were investigated. As the Jex increases, writability increases due to the increase of the interlayer exchange coupling but over-all SNR decreases due to the reversed grains in a bit. The increase of the SHL thickness improves writability, but causes SNR to decrease. As Ku of the SHL decreases, both writability and SNR increase. The reduction of Ku of the SHL is important to get high SNR and good writability. Magnetically well-isolated grains in the SHL are apt for high SNR in exchange-coupled composite media.