Kerr Enhancement by Layer Modulation in Co/Pt Multilayers

Thus far, a good Kerr hysteresis loop has been obtained only for thickness ratios of Co to Pt lower than 0.6 in Co/Pt multilayers. It has been found in this study that perfect squareness can be obtained for ultrathin films even with a high thickness ratio of t Co/t Pt=1. This is caused by diminished magnetostatic energy. Furthermore, layer-modulated structures were investigated in order to increase the Kerr rotation angle. The Co/Pt multilayers were prepared by two-source rf-magnetron sputtering. Co/Pt multilayers with perfect squareness were deposited with a Pt interlayer, which resulted in excellent magneto-optical properties. In particular, the Kerr rotation angle measured from the glass-substrate side showed a very large value, 0.73 degrees. This Kerr enhancement is due to optical interference and multiple reflection. On the other hand, another interesting phenomenon was also obtained. Kerr hysteresis showed characteristic stepwise hysteresis loops when the interlayer Pt thickness was increased. Such layer-modulated multilayers have potentiality for high-density magneto-optical recording.