Single-pass recording of multilevel patterned media

Abstract

A method of performing data / information recording and retrieval utilizing a multilevel patterned magnetic medium, comprises: (a) providing a magnetic recording system including a read / write head and a multilevel patterned magnetic recording medium including a plurality of spaced apart elements each comprising a stacked plurality n of magnetic recording cells with different magnetic properties and magnetically decoupled from overlying and / or underlying cells; (b) providing relative movement between the write head and magnetic recording medium; and; (c) writing to the medium by supplying the write head with a modulated write current comprising a plurality n of pulses of different magnitudes while the head moves past each element, thereby applying n different magnetic field strengths to each element, the write current including a first pulse of magnitude sufficient to write to a first cell of each element having a highest magnetic coercivity of said cells, and n−1 succeeding pulses of progressively smaller magnitude for sequentially writing to the remaining n−1 lower magnetic coercivity cells of each element but of insufficient magnitude to write to progressively higher magnetic coercivity cells; whereby the writing occurs in a single pass of the write head past each element.

Description

FIELD OF THE INVENTION[0001]The present invention relates to an improved method of recording data / information on multilevel patterned magnetic recording media comprising an array of discrete magnetic elements each including a stacked plurality of magnetic recording levels, and to improved media and systems therefor. The invention enjoys particular utility with hard disk-based, very high areal recording density magnetic data / information storage systems utilized in computer-related applications.BACKGROUND OF THE INVENTION[0002]Designers, manufacturers, and users of electronic computers and computing systems require reliable and efficient equipment for storage and retrieval of information in digital form. Conventional storage systems, such as magnetic disk drives, are typically utilized for this purpose and are well known in the art. However, the amount of information that is digitally stored continually increases, and designers and manufacturers of magnetic recording media work to inc...

AI Technical Summary

Benefits of technology

[0021]An advantage of the present invention is an improved method of performing data / information recording and retrieval utilizing a multilevel patterned magnetic medium.

[0022]Another advantage of the present invention is an improved multilevel patterned magnetic recording medium.

[0023]Yet another advantage of the present invention is an improved magnetic data / information recording and retrieval system.

[0024]Additional advantages and other aspects and features of the present invention will be set forth in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.

[0025]According to an aspect of the present invention, the foregoing and other advantages are obtained in part by an improved method of performing data / information recording and retrieval utilizing a multilevel patterned magnetic medium, comprising steps of:

[0026](a) providing a magnetic recording system including a multilevel patterned magnetic recording medium (preferably a disk-shaped medium) and a write head, the medium including a plurality of spaced apart elements, each element comprising a stacked plurality n of magnetic recording cells each with different magnetic properties, each cell magnetically decoupled from overlying and / or underlying cells;

Problems solved by technology

(1) there is an infinite number of possibilities for the magnetic moments of the continuous magnetic film, and as a consequence, the write head must be able to write very precisely in order to precisely define, without error, the magnetic moment, location, and area of each bit on the magnetic film;

(2) since the continuous film tends to link exchange and magnetostatic interaction between neighboring magnetic bits, when the bits are very close, writing of one bit can result in writing of neighboring bits because of the exchange and magnetostatic interaction, causing errors in reading;

(3) the absence of physical boundaries between many bits of the continuous magnetic film cause the writing and reading process to occur in a “blind” fashion, i.e., the location of each bit is determined by calculating the movements of the disk and the read or write heads instead of physically sensing the actual bit location;

(4) the boundaries between adjacent pairs of bits tend to be ragged in continuous magnetic films, resulting in noise generation during reading; and

(5) the requirement for increased areal recording density has necessitated a corresponding decrease in recording bit size or area. Consequently, recording bit sizes of continuous film media have become extremely minute, e.g., on the order of nanometers (nm). In order to obtain a sufficient output signal from such minute bits, the saturation magnetization (Ms) and thickness of the film must be as large as possible. However, the magnetization quantity of such minute bits is extremely small, resulting in a loss of stored information due to magnetization reversal by “thermal fluctuation”, also known as the “superparamagnetic effect”.

However, further decrease in grain width in perpendicular media necessitated by increasing requirements for areal recording density will inevitably result in onset of the superparamagnetic effect even for such type media.

The superparamagnetic effect is a major limiting factor in increasing the areal recording density of continuous film magnetic recording media.

Superparamagnetism results from thermal excitations which perturb the magnetization of grains in a ferromagnetic material, resulting in unstable magnetization.

As the grain size of magnetic media is reduced to achieve higher areal recording density, the superparamagnetic instabilities become more problematic.

When this inequality is not satisfied, thermal energy demagnetizes the individual magnetic grains and the stored data bits are no longer stable.

Consequently, as the magnetic grain size is decreased in order to increase the areal recording density, a threshold is reached for a given Kμ and temperature T such that stable data storage is no longer possible.

While fabrication methods supporting element or dot densities up to about 300 Gbit / in2 have been demonstrated, large area ultra-high density magnetic element patterns necessary for Tbit / in2 recording densities are currently unavailable or not achievable in a cost effective manner.

A disadvantage inherent with practical use of the multilevel continuous film media of e.g., U.S. Pat. No. 5,583,727, is that the number of magnetic grains, and hence the read signal and media noise, are divided into the multiple levels, thereby degrading the signal-to-media noise ratio (SMNR).

However, a disadvantage of the proposed scheme for utilizing multilevel patterned media arises from the requirement that each level be addressed individually.

However, it is evident that for such a write procedure the data rate disadvantageously incurs a substantial decrease.

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