Noise properties of multilayered Co-alloy magnetic recording media

The results of the medium-noise characterization of multilayered magnetic recording films having thin nonmagnetic isolation layers are presented. A substantial reduction of all types of medium noise was found for several Co alloys when multilayered. This reduction in noise power is approximately proportional to 1/(number of magnetic layers) but also depends on film thickness and other factors. The primary cause of the reduction is evidently the breaking of exchange between magnetic layers. It is also found that the intrinsic noise power per unit varies with film thickness, more in some alloys than in others, altering the noise reduction for multilayers. Evidence also suggests that magnetostatic interactions between layers further reduce the noise power. A phenomenological model explaining the observed effects is presented. The evidence suggests that a similar effect would be observed in any metal-film recording medium