Effects of stacking faults on magnetic viscosity in thin film magnetic recording media

There is much interest in crystallographic defects in thin film magnetic re cording media and their role in influencing recording performance such as m edia noise and thermal loss. In this article we report a correlation betwee n the magnetic viscosity in CoPtCr thin film media, which is the origin of thermal loss effects, and the concentration of local fcc-like regions. The concentration of these defects (the type and density of stacking faults) wa s varied by growth on different underlayers (Cr and CrTa/Cr) and was measur ed with grazing incidence x-ray scattering using synchrotron radiation. We show that a substantial percentage of local fcc regions in an otherwise hcp cobalt alloy film leads to significant magnetic viscosity effects at quite modest magnetic fields. We find that the activation volume is reduced for a sample with a higher percentage of fcc-like regions and suggest that this can be understood in terms of the effect of weak links acting to stabilize local micromagnetic configurations. (C) 1999 American Institute of Physics . [S0021-8979(99)04504-1].