The role of dipolar interactions in AFC-media

We have experimentally studied the role of dipolar interactions in antiferromagnetically coupled (AFC) recording media. In addition to the antiferromagnetic interlayer exchange coupling, recorded transitions lead to dipolar interactions between the two magnetic layers, which also favor an antiparallel alignment of the magnetization for longitudinal recording media. For low recording densities, we find a strong increase of the bias field that is acting upon the lower layer with increasing transition density. At an intermediate density, this bias field exhibits a maximum, gaining about 300 Oe over the DC case and slowly decreases upon further increase of the recording density. Our experimental results are in good agreement with model calculations that take both, the dipolar inter- as well as intralayer contributions into account.