Exchange coupled perpendicular media

TL;DR

This paper reviews exchange spring bilayers and graded media for magnetic storage, presenting an analytical model for optimization, demonstrating improved thermal stability and reduced switching field distribution, enabling ultra-high density data storage.

Contribution

It introduces an analytical model for optimizing graded media and demonstrates the advantages of exchange spring bilayers and graded media over single phase media.

Findings

Optimal magnetic polarization Js = 0.8 T for graded media.

Supports ultra-high density storage up to 10 Tbit/in^2.

Significant reduction in switching field distribution in bilayer and graded media.

Abstract

The potential of exchange spring bilayers and graded media is reviewed. An analytical model for the optimization of graded media gives an optimal value of the magnetic polarization of Js = 0.8 T. The optimum design allows for thermally stable grains with grain diameters in the order of 3.3 nm, which supports ultra high density up to 5 to 10 Tbit per inch2. The switching field distribution is significantly reduced in bilayer media and graded media compared to single phase media. For the graded media the switching field distribution is reduced by about a factor of two. For bilayer media the minimum switching field distribution is obtained for soft layer anisotropies about one fifth of the hard layer anisotropy. The influence of precessional switching on the reversal time and the reversal field is investigated in detail for magnetic bilayers. Exchange spring bilayers can be reversed with field pulses of 20 ps.