The magnetic properties and thermal stability of antiferromagnetically coupled (AFC) media with thin Co interlayers are investigated. Since the thermal stability is strongly dependent on the exchange coupling constant J(ex) in the AFC media, the thin Co interlayers were inserted on both interfaces of the Ru layer to obtain higher values of J(ex). The J(ex) above 0.6 erg/cm(2) was obtained in the AFC media with the Co interlayers above 1 nm in comparison with about 0.1 erg/cm(2) in AFC media without the Co interlayers. The thermal stability of the AFC media with Co interlayers was greatly improved over those of the AFC media without Co interlayers.