Reduction of Co-Cr-Pt media noise by addition of Ti to Cr underlayer

Effects of Ti addition to a Cr underlayer on the magnetic and crystallographic properties of Co-Cr-Pt media were investigated. C/Co-C-20-Pt (Pt: 8 and 12 at. %)/CT-Ti (Ti: 0-30 at. %) films were deposited on textured Ni-P/Al-Mg substrates by de magnetron sputtering. In-plane H-c and S* increased as Ti was added to the Cr underlayer. The media noise at 167 kFCl decreased with an increase of the Ti content from 0 to 20 at. %. The normalized media noise of Co72Cr20Pt8/Cr75Ti25 media was 20% lower than that of Co68Cr20Pt12/Cr90Ti10 media where their coercivity and S* were almost the same. Further increase of the Ti caused the increase of the media noise. Transmission electron microscopy studies showed that average grain size of Cr-Ti films decreased from 30 to 20 nm with the increase of the Ti content from 0 to 20 at. %. The activation volume of Co68Cr20Pt12 films measured from the time dependences of remanence coercivity decreased by 30% as the Ti content increased from 0 to 20 at. %. The reduction of media noise is probably due to the decrease of the magnetic switching volume which is caused by the reduction of the grain size of Cr-Ti underlayers. (C) 1996 American Institute of Physics.