First order reversal curves (FORC) method has been reported to be an efficient tool to study
interaction between grains and layers of magnetic materials. Although a few studies have been
carried out on perpendicular recording media in the past, a study on the effect of systematic
variation of exchange interaction in granular perpendicular magnetic recording media on FORC
contours has not been carried out in detail. Such a study will help to understand the use of FORC
better. In this paper, we have made a systematic set of samples in order to study the variation in
exchange coupling and its effect on FORC contours. The pressure during the deposition of the
second ruthenium layer and the magnetic layer was varied to alter the separation between the
grains and hence the exchange interaction between the grains in the CoCrPt-oxide recording layer.
In addition, the thickness of Co-alloy cap layer was used as an additional tool to control the
exchange interaction between the magnetic grains. The results indicated that the interaction field
obtained from the FORC does not vary in a significant manner when the changes in exchange interaction
are small. In comparison, the peak intensity of the FORC shows a clear trend as the
exchange coupling is varied, making it a more suitable parameter to study the exchange and magnetostatic
interactions in systems such as magnetic recording media.