Investigation on the origin of switching field width in Co-Pt dot array

The switching field width (SFW) in bit-patterned media is one of the important factors affecting the recording performance. The origin of SFW in Co80Pt20 magnetic dot array patterned by electron beam lithography was investigated. The SFWs of dot arrays with a dot size of 29 nm and period of 40–100 nm were measured from element-specific magnetic hysteresis curve based on xray magnetic circular dichroism. The experimentally obtained SFWs suggested that the intrinsic SFW caused by the distribution in structural and magnetic properties of each dot is 1.2 kOe when additional magnetostatic interaction between the dots is assumed. Distribution in the dot size was investigated as one of the causes of the intrinsic SFW. However, it was estimated that a dot size distribution of 1 nm broadens the SFW by 0.14 kOe which is only about 12% of the intrinsic SFW. Primary cause of the intrinsic SFW should be attributed to others.