The Magnetic properties and recording performances of CoCrTa/Ti/M (M: CoZrNb, Fe, Co) double-layered perpendicular recording media were studied. It was revealed that a thin Ti film of 5 nm gave the most enhanced c-axis alignment perpendicular to the film plane in media with CoZrNb or Fe back-layers, resulting in the highest coercivity and squareness of CoCrTa. The recording performance of media with Fe back-layers, using a single-pole-type writing head, indicated that a thinner back-layer with a high flux density can be used without any reduction of the recording sensitivity and resolution, even though the Fe back-layers do not have good soft magnetic properties. However, hcp-Co back-layers degrade the recording sensitivity and resolution. The media noise of media with Fe or Co back-layers was significantly higher than that of CoZrNb back-layer media. It is suggested that these noise spectra are related to the domain structure of the back-layers.
