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Superconducting Directed Field Electromagnet for Magneto-Optics

IP.com Disclosure Number: IPCOM000034401D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Paul, DI: AUTHOR [+3]

Abstract

A problem in magneto-optic recording is the application of a biasing magnetic field to the writing laser spot on the recording media at rates high enough to accomplish overwrite, thus avoiding an extra erase pass. Usually, the switching of the magnetic bias field is limited by the large inductance of the electromagnet. High switching rates of the bias field could be achieved if a superconducting open torus was used to contain and direct the bias field. One such configuration is shown in the figure for application to a disk-shaped recording media. The torus 1 contains a single loop of superconducting wire 2 placed next to the inside the torus but separated from it by a thin insulating layer to prevent shorting and Josephson effects.

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Superconducting Directed Field Electromagnet for Magneto-Optics

A problem in magneto-optic recording is the application of a biasing magnetic field to the writing laser spot on the recording media at rates high enough to accomplish overwrite, thus avoiding an extra erase pass. Usually, the switching of the magnetic bias field is limited by the large inductance of the electromagnet. High switching rates of the bias field could be achieved if a superconducting open torus was used to contain and direct the bias field. One such configuration is shown in the figure for application to a disk-shaped recording media. The torus 1 contains a single loop of superconducting wire 2 placed next to the inside the torus but separated from it by a thin insulating layer to prevent shorting and Josephson effects. A current I is passed through the wire and the resulting magnetic field is contained and directed within the superconducting torus by the Meisner effect. The inductance is lower than a conventional electromagnet because of the reduction in the number of turns of the coil. The field can be directed by forming and necking the openings of the torus 3 to achieve the desired application location and flux density. The field can be applied to both sides of the recording medium at once as shown in the figure. Because the torus is hollow, small openings can be made at the proper location 4 to admit laser light to shine on the recording media in the same location as the bias field,...