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, DeltaSFD, from the difference between the DCD and M-DCD curves, and defined them as DeltaH_r/H_r (at ~ 10 Oe/s) and DeltaH_r ^P/H_r ^P (at ~10⁸ Oe/s). The values of DeltaSFD characterized by subtracting the effect of thermal agitation, DeltaH ₀/H₀, were nearly half those of DeltaH_r /H_r for 10-nm-thick media. DeltaH₀/H₀ 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 DeltaH₀/H₀ was probably caused by an increase in the stacking fault density and the formation of fcc layers in the hcp CoPtCr lattice. A simple calculation based on the coherent switching of magnetization revealed that the c-axis distribution results in DeltaH ₀/H₀ of about 0.08, independent of Pt content. These results suggest that the DeltaSFD due to the grain-to-grain anisotropy field variation was small, only 0.02-0.03