The calculation of output time decay in very-thin film disks

Abstract

Low noise media are , q u i d together with recent MR or Spin-valve heads for high density applications. To decrease the media noise, the magnetic unit, which is a grain or the activation volume in the film, must be shrunk. It is well known that the smaller the magnetic unir, the more susceptible it is to thermal fluctuations. This results in magnetization decay and in the broadening of the magnetic transition length “a” in a recorded medium. Both result in output decay. Under an assumption that magnetization maintains an arctan distribution, we can estimate “a” from the slope of the Mr distribution (and dHx/dx(x=0)) as a function of time 1, energy barrier BE and its distribution, temperature, and the magnetic properties ofthe media. Using the Mr decay data and the Anhenius equation [l], we determined the mean value and its standard deviation a. Therefore, the output decay with time for various recording densities can be estimated. We found fair agreement between calculations and experiments at low recording densities.