Pt content dependence of the switching field distributions of CoPtCr-SiO₂ perpendicular media characterized by subtracting the effect of thermal agitation

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 ΔH_r/H_r (at ∼ 10 Oe/s) and ΔH_r^P/H_r^P (at ∼10 ⁸ Oe/s). The values of ΔSFD characterized by subtracting the effect of thermal agitation, ΔH_o/H_o, were nearly half those of ΔH_r/H_r for 10-nm-thick media. ΔH_o/H_o 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 ΔH_o/H_o 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/H_o 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.