Optimization of the SiO2 content in CoPtCr-SiO2 perpendicular recording media for high-density recording

Optimization of the SiO2 content for high-density recording was discussed for {(Co90Cr10)(80)Pt-20}(100-Z0)-{SiO2 }(Z) perpendicular recording media. The grain size D-grain decreases significantly from 8.8 to 5.4 mn as the SiO2 content Z increases from 0 to 14.4; however, no significant difference in c-axis orientation was observed. Magnetocrsytalline anisotropy of grains maintains a large value of nearly 8 x 10(6) erg/cm(3), even at 10 at % SiO2 addition, indicating a high potential of perpendicular anisotropy K-u to resist thermal agitation of magnetization. The coercivity H-c increases significantly as the SiO2 increases, which is coincident with the reduction of the slope of magnetization curve alpha = 4pi(dM/dH) due to the enhancement of grain isolation. The H, shows a maximum at around 11 at % SiO2 (nearly 30 vol % SiO2). A further increase of SiO2 reduces the value of H-c significantly, although the a maintains a constant value of nearly 2, due to thermal agitation of magnetization. The media noise reduces significantly as the SiO2 increases; however, the addition of SiO2 beyond about 13 at % leads to a slight increases in media noise probably due to a significant increase of thermal agitation. The recording resolution D-50 shows a broad maximum of similar to 420 kFCI at around 11 at % SiO2, suggesting that the D50 is related to the media noise performance. Experimental results indicate that there is a tradeoff to be made between the thermal stability and media noise performance as a function Of SiO2 Composition.