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Hard Magnetic Films: Preparation and Applications

IP.com Disclosure Number: IPCOM000083644D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Ahn, KY: AUTHOR [+2]

Abstract

Hard magnetic films (high H(c) films) are required for high-density recording in tapes and discs, and also for applications as a bias magnet. An example for the latter use is a self-biased magnetoresistive sensor as sketched in the figure. The hard film exerts a magnetic field to the soft sensor film; the magnitude of this bias field being dependent upon the magnetization, thickness, and width of the hard film.

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Hard Magnetic Films: Preparation and Applications

Hard magnetic films (high H(c) films) are required for high-density recording in tapes and discs, and also for applications as a bias magnet. An example for the latter use is a self-biased magnetoresistive sensor as sketched in the figure. The hard film exerts a magnetic field to the soft sensor film; the magnitude of this bias field being dependent upon the magnetization, thickness, and width of the hard film.

The composition of the hard film is either CoNi or Co where the concentration of Co is between 70 and 100 percent by weight. In this range of composition, the magnetocrystalline anisotropy energy is very large, of the order of 10/5/ ergs/cm/3/ in hcp phase vs. 10/4/ ergs/cm/3/ found in cubic-phase materials. This high energy can be converted to large values of H(c).

The growth of the hexagonal phase using this composition range is to grow epitaxially films of Au, Ag, or Cu onto single-crystal substrates, followed by the deposition of magnetic film. Magnetic films deposited onto certain substrates tend to have more hexagonal-close pack structure and give rise to large H(c).

Examples of such films are shown below. Gold films of 2,000 angstroms thickness are simultaneously deposited onto a variety of single-crystal substrates, cubic (100) orientation, which are heated to temperature in the range of 200 to 300 degrees C. Typical evaporation rate is 30 angstroms in a background pressure of 3 x 10/-7/ torr. Magne...