The effects of oxygen on intergranular exchange and anisotropy dispersion in CoPd multilayers for perpendicular magnetic recording media

A typical way to analyze anisotropy dispersion (σHk) in perpendicular magnetic recording media is to simply calculate the slope parameter α (dMdH) from a hysteresis loop. However, α is also dependent on intergranular exchange, and is therefore not an accurate measure of σHk. In this work, σHk and intergranular exchange were varied in high coercivity CoPd multilayers on InSn seed layers in order to determine their relationship with coercivity, saturation magnetization, and α. These parameters were altered using various concentrations of oxygen as measured by Auger sputter depth profiles, and a minor loop coercivity method was used to find σHk independent of exchange. A general cross-referencing analysis was developed to characterize the important parameters of media using hysteresis loops. And in this study, the analysis showed that oxygen in Co-Pd multilayers reduced intergranular exchange coupling as expected, but it also increased σHk at higher concentrations.