In this paper we report the results of our investigations into interaction effects in Co metal alloy thin films. We have studied, through measurement and comparison of remanence curves, the effects of variable underlayer and magnetic layer thicknesses. Our results indicate a strong correlation between the magnitude of cooperative switching and measured signal-to-noise. Through analysis of the irreversible susceptibility, χirr, we have also been able to distinguish the relative degree of quasi-particulate and exchange coupled behaviour within each film. © 1991.