Co/Pt and Co/Pd multilayers as magneto-optical recording materials

Abstract The magneto-optical and magnetic properties of Co/Pt and Co/Pd multilayers for magneto-optical recording materials are described. Thick multilayers do not have an adequate Kerr loop for MO recording because of forming a stripe domain configuration in the remanent magnetization. However, thin films below a few hundred angstrom exhibit a perfect square Kerr loop as interpreted by domain theory. The Kerr rotation is enhanced at the ultrathin region by optical interference and multiple reflection, and the enhancement is remarkable especially at wavelengths above 500 nm. The coercivity of the ultrathin films increases to between one and several kOe by the sputtering gas conditions and the under layers of fcc metal atoms, originating from a change in the film morphology and an increase in the perpendicular magnetic anisotropy, respectively. These ultrathin multilayers having large Kerr rotation at shorter wavelengths and high corrosion resistance are promising candidates for high density MO recording. The magneto-optical disks using 2P pre-grooved glass substrate showed carrier-to-noise ratios of 53 and 46 dB at 780 nm for Co/Pt and Co/Pd media, respectively. Regular and clear bit domains were observed and completely erased thermomagnetically.