Relaxation of written transitions in thin films with perpendicular magnetic anisotropy (abstract)

Abstract

We have measured the rate at which recorded signals decay in Co78Cr17Ta5 alloys, Co70Cr15Ta5Pt10 alloys, and Pd/Co multilayers. At low write frequencies, the magnetization decay resembles that observed by magnetometry. At high write frequencies, the relative decay rate decreases substantially. This is attributed to a change in the demagnetizing energy associated with high linear densities in perpendicular media. A model for magnetization decay is used to deduce the activation volume, the size distribution, and the barrier to flux reversal that exists for the alloy films. A time scale tε is introduced, over which the decay rate is dominated by the initial condition applied by the write head. The observed decay in the multilayers was much lower (<0.5%/time decade) than in the alloys (3%–4%/time decade) at all of the spatial frequencies tested.