Ultra-high density recording technologies

The Engineering Research Center in Data Storage Systems at Carnegie Mellon University in cooperation with the National Storage Industry Consortium has selected goals of achieving 10 Gbit/sq in. recording density in magnetic and magneto-optic disk recording and 1 terabyte/cubic in. magnetic tape recording technologies. This talk describes the approaches being taken and the status of research leading to these goals

Approaches to 100 Gbit/sq. in. recording density

A recording density of 10 Gbit/sq. in. is being pursued by a number of companies and universities in the National Storage Industry Consortium. It is widely accepted that this goal will be achieved in the laboratory within a few years. In this paper approaches to achieving 100 Gbit/sq. in. storage densities are considered. A major obstacle to continued scaling of magnetic recording to higher densities is that as the bit size is reduced, the grain size in the magnetic media must be reduced in order that media noise does not become so large that the signal to noise ratio (SNR) degrades sufficiently to make detection impossible. At 100 Gbit/sq. in., the bit size is only 0.006 square micrometers, which, in order to achieve 30 dB SNR, requires a grain size of about 2.5 nm. Such small grains are subject to thermal instability, and the recorded information will degrade over time unless the magnetic anisotropy of the materials used is increased significantly, or the media thickness is made much larger than expected on the basis of scaling today's longitudinal media thickness

Micromagnetic characteristics of transverse diffuse domain boundaries in permalloy thin films

Transverse domain boundaries propagating in the longitudinal direction at speeds one to three orders of magnitude faster than normal domain walls are responsible for most of the lower speed reversals in magnetic thin films. Using a 10-ns exposure time Kerr magnetooptic camera, these boundaries have been photographed for a variety of applied fields in several films with thicknesses ranging from 500 to 3500 Å. High-magnification photographs of the boundary transition region reveal that the boundaries consist of small isolated areas of reversed and partially reversed magnetization in a nonreversed background. Propagation occurs by the nucleation of additional small areas of reverse magnetization within and ahead of the transition region. In a given film the width of the transition region increases as the applied field is increased. By approximating the divergence of the magnetization at the boundary as a line charge, a model has been derived which predicts the boundary widthWto beW = \frac{8M_{s}t}{H_{n}}\frac{1}{(1-H/H_{n})}where Msis the saturation magnetization andHis the applied field. The nucleation threshold Hnis the threshold at which nucleation is observed over all the film. The experimental data fit this predicted dependence quite well. The rapid increase in width of the transition region with applied field is correlated with a rapid nonlinear increase in the velocity of propagation