The effect of interlayer thickness on the magnetic properties of exchange-coupled composite media has been studied. Films consisting of a CoPtO hard magnetic layer and a CoCrPt soft layer separated by a Pt interlayer with a thickness varying from 0to40Å have been fabricated. At low Pt thicknesses (⩽16Å) the exchange coupling forces the layers to switch as a single unit with a reduction in the hard magnetic layer coercivity of >2.5kOe. Thicker Pt layers induce sufficient decoupling to permit each layer to reverse separately. The variation of the coercivity with Pt thickness is complex and suggests that the coupling between the layers is a combination of dipolar and exchange effects.