Effect of nonmagnetic underlayer on structural and magnetic properties of CoCr-alloy thin film media

Microstructures of CoCr-alloy thin film media were investigated by cross-se ctional transmission electron microscopy focussing on the initial growth re gion of the magnetic layer grown on nonmagnetic underlayers. An introductio n of nonmagnetic hcp-CoCrRu layer between an hcp-CoCrPt recording layer and an hcp- or a bcc-underlayer improved the crystallographic quality of the i nitial growth region. Sharp compositional distributions of alloying element s at the interfaces of a CoCrPt/CoCrRu/CrTi perpendicular medium and a CoCr Pt/CoCrRu/CrTi longitudinal medium were respectively confirmed by electron energy loss spectroscopy employing a finely focussed electron beam. Coerciv ity and squareness of the thin film media increased by realizing good heter o-epitaxy between the nonmagnetic and the magnetic hep-layers.