Anisotropy Graded Media: Extending the Superparamagnetic Limit (abstract)

Abstract

The maximum storage density in magnetic media is limited by the superparamagnetic size of the grains that make up the bits. The superparamagnetic size can be reduced by increasing the anisotropy of the grains; however, in conventional media, in which the anisotropy of the grains is uniform, this leads to a proportionate increase in the switching field. The switching field, however, is limited by the maximum magnetization of the core material in the write head. Recent calculations have shown that the switching field can be significantly reduced relative to the thermal stability of the grains if the anisotropy is made to vary appropriately from the bottom to the top of the grain. In this project we propose to test this concept by fabricating and characterizing anisotropy graded films. We will use the hcp CoPtX system, with X = Cr or Ru, where the anisotropy gradient is obtained by grading the composition. Both sheet films and granular films will be fabricated. The anisotropy gradients will be determined by analyzing magnetization curves. Dynamic coercivity measurements will be used to determine the short-time coercivity and the zero-field energy barrier in the granular films. These results will be compared with similar measurements on films with uniform anisotropy films in order to test the predictions for graded media.

Description
Keywords
Educational assessment, Abstracts, Thermodynamic states and processes
Citation
Horton, K., et al. (2009): Anisotropy Graded Media: Extending the Superparamagnetic Limit (abstract). AIP Conference Proceedings, 1119(1). DOI: https://doi.org/10.1063/1.3137820