Both the isothermal remanent magnetization and the dc demagnetization remanence were measured on thin films of CoCr with a perpendicular anisotropy energy suitable for perpendicular recording media. The measurements were made with two applied magnetic field geometries, parallel and perpendicular to the film plane. Plots of the dc demagnetization remanence versus the isothermal remanent magnetization were used to determine the presence of interactions for both applied magnetic field geometries. As expected, the perpendicular magnetization process is dominated by the demagnetization field. When the data are corrected for the demagnetization field, a residual negative interaction is found from the perpendicular data. This negative interaction was also observed in the parallel applied field geometry plots, where the demagnetization factor is negligible. The success of the analysis, using a mean-field approximation to model the interactions, which in this case is the demagnetization field, suggests a general technique to quantify interactions in magnetic systems.