Magnetic Storage: Principles and Trends

Abstract

Magnetic recording can store digital information at an areal density well beyond the fundamental density-limit of optical systems. The central problems in achieving high trans-optical information density with magnetic recording reside primarily in the materials area. In addition to improved magnetic properties, such as head materials with high saturation magnetization and recording media with low noise and high coercivity, tribological considerations impose constraints on the ultimate density that will be attained. The exponential loss of signal due to spacing between the head and recording medium is inherent in all magnetic recording, necessitating the development of durable quasi-contact interfaces.Magnetic recording is the universal technology for electronic information mass storage. Its presence is ubiquitous as audio tapes, VCRs, floppy disks, computer hard disks, credit cards, etc. Sales of magnetic recording products exceed $50 billion annually, with strong growth projected into the foreseeable future. A steady progression in storage density and corresponding reduction in cost has characterized all phases of magnetic recording; the literature is replete with historical and projective curves showing cost and density numbers. Computer disk file memories have doubled in areal density every 2.5 years for about the past 30 years. Although many competing technologies have been proposed through the years, none has been able to displace or even significantly impact magnetic recording. The first challenge was thermoplastic recording, followed by at least three resurrections of magneto-optic recording, bubbles, semiconductors, and various nonmagnetic optical storage devices.