Experimental and theoretical analysis of rotational hysteresis loss in CoCrTa perpendicular recording media

We measured the value of rotational hysteresis loss W_r for various CoCrTa perpendicular media, and discussed the dependence of W_r and the hysteresis integral R_h on the perpendicular anisotropy and the strength of intergranular exchange coupling. Simulated results using a model based on the Landau-Lifshitz-Gilbert equation were compared with the experimental results. The experimental and theoretical studies revealed that improvement of the c-axis alignment significantly reduces W_r, resulting in a small R_h value of ~0.2. Increase of intergranular exchange coupling shifts the applied field at which W_r reaches a maximum, H_p, to a lower field and produces a large R_h. Decrease of K_u also shifts H _p to a lower field but is accompanied by a reduction of R_h. These results imply that the values of R_h and H_p are strongly related to the structural and magnetic properties, and analysis of rotational hysteresis loss appears to be a useful technique to characterize perpendicular media