The influence of ion-milling damage to magnetic properties of Co ₈₀Pt₂₀ patterned perpendicular media

In this study, different accelerating voltages were applied in the ion-milling process to fabricate CoPt nanopillar arrays in order to investigate the influence of ion damage to magnetic properties. Nanopillar arrays fabricated at a higher accelerating voltage give a lower value of coercivity and ion damage does not broaden the switching field distribution (SFD). The 'edge damage' model was employed in micromagnetic simulations to investigate the reversal mechanism and SFD. The results shows that the edge damage can change the switching mode from coherent rotation to nucleation followed by rapid domain wall motion, and the broad SFD mainly comes from the intrinsic anisotropy distribution, rather than size distribution. In addition, the angle dependence of the switching field measurement shows that nanopillars with damaged edges have Stoner-Wohlfarth behaviour, which indicates that fitting the Stoner-Wohlfarth curve does not necessarily mean coherent rotation. It is the comparison between the field for domain wall motion and the nucleation field that determines the location of angle dependence curves.