Switching field distribution of CoPtCr-SiO2 perpendicular recording media obtained by subtracting thermal agitation of magnetization

The effect of thermal agitations on the switching field distribution (SFD) of CoPtCr-SiO2 perpendicular media was investigated, and the intrinsic SFD caused by variations in the grain-to-grain switching field was determined. DC demagnetizing (DCD) magnetization curves and minor DCD (M-DCD) magnetization curves were measured at applied field-sweep rates of similar to 10 Oe/s and similar to 10(8) Oe/s. We estimated the SFD from the difference between the DCD and M-DCD curves, and defined them as Delta H-r/H-r (at similar to 10 Oe/s) and Delta H-r(P)/H-r(P) (at similar to 10(8) Oe/s). The values of Delta H-r/H-r were much larger than those of Delta H-r(P)/H-r(P). Moreover, Delta H-r/H-r. increased faster than Delta H-r(P)/H-r(P) as the thickness decreased, suggesting that the SFD measured at vibrating Sample magnetometer (VSM) time scales is significantly influenced by thermal agitation. The intrinsic SFD estimated using a series of media with various film thicknesses was about 0.14, which was 55%-75% of Delta H-r/H-r for 8-16-nm-thick media. An analysis of the temperature dependence of Delta H-r/H-r supported this conclusion. It is concluded that the SFD measured at VSM time scales is significantly influenced by thermal agitation of the magnetization, and the intrinsic SFD is likely to be nearly half that measured at VSM time scales.