Magnetic and Magneto-Optical Properties of Sputtered Co/Pd Multilayers

Co/Pd multilayer thin films consisting of Co layers between 2-25 Å and Pd layers of typically 14 Å were prepared by rf sputtering. Hysteresis loops and the magnetization were measured parallel and perpendicular to the film plane. From these measurements and torque curves it was found that the multilayers show a transition of the easy axis from an in-plane to a direction perpendicular to the film plane when decreasing the Co layer thickness below 10 to 6 Å depending on the sputter rate and sputter gas used (Ar or Kr). Below 4.5 Å Co layer thickness M_r/M_s is nearly one. The coercivity increases with decreasing Co layer thickness also depending on the sputter parameters used and the thickness of the seedlayer. The hysteresis loops measured with the Kerr-tracer did not show much difference with those measured with the VSM. Although TEM photographs show very clearly a layered structure when a seedlayer is used, low angle X-ray measurements seem to indicate sharper interfaces in multilayers where no or a very thin seedlayer is used. From the recording point of view the best results (high coercivity, squareness and anisotropy) were obtained by using Ar gas at high pressure.