Technologies for Image Information Storage. A Study of Nonuniformly Spaced Transversal Filters for Digital Magnetic Recording.

Magnetic recording has been the dominant recording technology for information storage since the invention of the computer. Currently, 1-Gbit/in. longitudinal magnetic recording (LMR) systems have been realized and densities of 10 Gbit/in., having bit areas less than 0.1 μm, are being developed. To reach this goal, a drastic scaling down of the track pitch, bit-cell length, head gap, medium thickness, and head-medium spacing is required. If this trend of increasing densities continues, an areal density of more than 300 Gbit/in. is predicted in the 21st century, based on computer simulation using the perpendicular magnetic recording (PMR) mode instead of the current LMR scheme. Magnetic-recording technologies and related materials have already been discussed in another issue of the MRS Bulletin, and hence in this paper, we concentrate on Co-Cr-X material used as a medium for PMR.The PMR mode has been studied since 1975 and at present, Co-Cr-X (e.g., X = Ta) films with perpendicular anisotropy are the most promising media material. In general, such media should have the following properties: easy axis of magnetization perpendicular to the film plane, suitable coercivity (Hc) and remanent magnetization (Mr) for storing the information and reading it at a high signal-to-noise (S/N) level, uniform columnar size with a small diameter, magnetically uncoupled columns having a magnetization reversal based on rotation instead of a domain-wall motion, chemical stability under various environmental conditions, and a small surface roughness. In order to achieve the desired magnetic anisotropy and coercivity, a columnar morphology (small diameter) with an hep [0001] texture and exchange-decoupled, columnar boundaries—to create a magnetic microstructure for single domain switching columns with high coercivity—should be obtained. An overview of the preparation, microstructure, and magnetic properties of Co-Cr thin films is given in Reference 8. Depending on the deposition parameters, a so-called initial layer (with an in-plane magnetization) can be present.

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Magnetic Recording Head Materials

MRS Bulletin ◽

10.1557/s0883769400036320 ◽

1996 ◽

Vol 21 (9) ◽

pp. 23-27 ◽

Cited By ~ 38

Author(s):

James A. Brug ◽

Thomas C. Anthony ◽

Janice H. Nickel

Keyword(s):

Magnetic Recording ◽

High Performance ◽

Disk Drive ◽

Information Storage ◽

Disk Drives ◽

Recording Heads ◽

Tremendous Amount ◽

The Media ◽

Materials Used ◽

Magnetic Recording Heads

The materials used in magnetic recording heads have recently received a tremendous amount of attention. This has been the result of a fortunate set of circumstances. Ever-increasing demands for information storage, especially for graphics-intensive applications, have necessitated unprecedented increases in disk-drive areal densities. Combined with this are recent discoveries in the area of magnetoresistive materials, enabling the design and fabrication of much more sensitive recording heads. The end result is a flurry of activity that has come to dominate the field of magnetics. This article will explore choices for magnetoresistive read head materials, with an emphasis on the materials challenges.The recording heads that are used in high-performance disk drives typically consist of separate magnetoresistive read and inductive write heads (see Figure 1) where previously a single inductive head performed both functions. Separation of the two heads allows each to be optimized for their individual function, an essential factor in enabling disk drives to contain gigabytes of storage. The write head is the simpler of the two, consisting of a U-shaped ferromagnet surrounding a set of coils. The ends of the ferromagnet are the magnetic poles defining the write gap. When current passes through the coils, a field bridges the gap, setting the orientation of the magnetization in the media. Information is stored by changing the polarity of the current in order to write a pattern of magnetic domains in the media. The materials used in write poles will be reviewed in the section, Write Head Materials.

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Particulate Recording Media

MRS Bulletin ◽

10.1557/s0883769400060188 ◽

1990 ◽

Vol 15 (3) ◽

pp. 53-62 ◽

Cited By ~ 24

Author(s):

M.P. Sharrock

Keyword(s):

Magnetic Field ◽

Magnetic Recording ◽

Rotating Disk ◽

Electrical Signal ◽

Optical Recording ◽

Information Storage ◽

Pulse Code Modulation ◽

Code Modulation ◽

Increasing Demand ◽

Phase Amplitude

Magnetic recording is a very useful and versatile technology, and one that is continuously evolving to serve the increasing demand for information storage and to meet the challenge of competitors such as optical recording. The basic principles of magnetic recording are described in detail elsewhere and briefly below.The elements of a magnetic recording system are a magnetizable surface layer carried on a flexible tape or on a rotating disk, and a transducer that can both write information to and read information from this surface. The tape or disk, often called a recording medium, and the transducer, called a head, move with respect to each other. The information to be stored is originally contained in an electrical signal, either by direct analog representation or via frequency, phase, amplitude, or pulse-code modulation. In response to this signal, the head in the writing mode generates an intense, localized magnetic field that is capable of changing the direction and degree of the magnetization in the surface material. Each time the input signal changes sign, the writing field changes direction and a transition between regions of opposite magnetization is created. As the head moves along the surface, a series of these transitions is created along a track. The resulting magnetization pattern of the tape or disk becomes itself the source of a spatially varying magnetic field.

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Technologies for Image Information Storage. A Development of a Video Hard-disk System for Hi-Vision Video Recording.

The Journal of The Institute of Image Information and Television Engineers ◽

10.3169/itej.52.1520 ◽

1998 ◽

Vol 52 (10) ◽

pp. 1520-1526

Author(s):

Toshiyuki Fujisawa ◽

Hiroki Minami ◽

Tatsuya Kurioka ◽

Haruo Okuda ◽

Junji Numazawa

Keyword(s):

Video Recording ◽

Hard Disk ◽

Information Storage ◽

Disk System ◽

Image Information

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Technologies for Image Information Storage. Electrostatic Torsion Mirror for Optical Heads.

The Journal of The Institute of Image Information and Television Engineers ◽

10.3169/itej.52.1507 ◽

1998 ◽

Vol 52 (10) ◽

pp. 1507-1512 ◽

Cited By ~ 1

Author(s):

Minoru Yonezawa ◽

Masayuki Sekimura ◽

Kiyotaka Uchimaru ◽

Norio Uchida ◽

Toshihiro Sugaya ◽

...

Keyword(s):

Information Storage ◽

Image Information

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The Future of Magnetic Recording

ASME 2001 Symposium on Nanotribology and Nanotechnology for 1Tbit/in2 ◽

10.1115/trib-nano2001-100 ◽

2001 ◽

Author(s):

Roger Wood

Keyword(s):

Magnetic Recording ◽

Hard Disk Drives ◽

Hard Disk ◽

Disk Drive ◽

Information Storage ◽

Limiting Factors ◽

Recording Technology ◽

Fundamental Limits ◽

Data Rates ◽

External Characteristics

Abstract Magnetic information storage technology has made astounding progress since its invention over a hundred years ago. For the last several years, storage packing densities in hard disk drives have doubled every year! This frantic pace is expected to soon slow because of the some very fundamental limits that are becoming increasingly evident in the technology. Conventional magnetic recording technology is expected to ultimately reach densities of several hundred Gigabits per square inch and data-rates of a few Gigabits/s (current products are ∼25 Gbit/sq.in. and over 0.5 Gbit/s). We examine the key limiting factors and then try to develop a consistent geometry and set of material properties that could support a density close to one Terabit per square inch. Finally we speculate about the external characteristics of a small hard disk drive that would store one Terabyte of information [1].

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