Thermal relaxation in antiferromagnetically coupled granular magnetic media

Using a conventional recording system we have characterized the thermally activated transition formation process in the lower layer of antiferromagnetically coupled magnetic recording media. We find that this thermal relaxation time depends strongly on the transition density, lower layer alloy composition, and layer thickness. A one-dimensional analytic model of coupled granular media that includes interlayer exchange, intergranular exchange, and magnetostatic energies is able to reproduce the observed results.