The switching field distributions (SFD) of CoPtCr-SiO2 perpendicular media as a function of Pt content were characterized by subtracting the effect of thermal agitation, and discussed in relation to the microstructure. DC demagnetizing (DCD) magnetization curves and minor dc demagnetizing (M-DCD) magnetization curves were measured at applied field sweep rates of ∼10 Oe/s and ∼108 Oe/s. We estimated the width of SFD, ΔSFD, from the difference between the DCD and M-DCD curves, and defined them as ΔHr/Hr (at ∼ 10 Oe/s) and ΔHrP/HrP (at ∼10 8 Oe/s). The values of ΔSFD characterized by subtracting the effect of thermal agitation, ΔHo/Ho, were nearly half those of ΔHr/Hr for 10-nm-thick media. ΔHo/Ho was about 0.10 at 10 at%Pt content, and increased as the Pt content increased, reaching 0.17 at 30 at%Pt content. The increase in ΔHo/Ho was probably caused by an increase in the stacking fault density and the formation of fee layers in the hep CoPtCr lattice. A simple calculation based on the coherent switching of magnetization revealed that the c-axis distribution results in ΔH o/Ho of about 0.08, independent of Pt content. These results suggest that the ΔSFD due to the grain-to-grain anisotropy field variation was small, only 0.02-0.03.
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