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Low Temperature Magnetic Field Induced Switch

IP.com Disclosure Number: IPCOM000122393D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+4]

Abstract

The application of an external magnetic field generally increases the electrical resistance of a metal film. In a normal metal, that is a non-superconducting metal such as copper, a magnetic field of 10 oersteds produces an increase of only a few parts per million (ppm) in resistance. In the case of a superconductor, operating close to the transition temperature (Tc), it is possible to increase the resistance from zero to the full normal state by the application of an external magnetic field, but it is not easy to produce a situation where the resistance of a metal film is decreased by the application of an external magnetic field. Examples of decreasing resistance in films by external magnetic fields exist and are caused by either magnetic impurities, or disorder in the film structure.

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Low Temperature Magnetic Field Induced Switch

      The application of an external magnetic field generally
increases the electrical resistance of a metal film.  In a normal
metal, that is a non-superconducting metal such as copper, a magnetic
field of 10 oersteds produces an increase of only a few parts per
million (ppm) in resistance.  In the case of a superconductor,
operating close to the transition temperature (Tc), it is possible to
increase the resistance from zero to the full normal state by the
application of an external magnetic field, but it is not easy to
produce a situation where the resistance of a metal film is decreased
by the application of an external magnetic field.  Examples of
decreasing resistance in films by external magnetic fields exist and
are caused by either magnetic impurities, or disorder in the film
structure.  In either case, the decrease is not sharp, and the
magnitude of the decrease is only a few ppm for an applied field of a
few Oersteds.

      Disclosed is a process whereby a small magnetic field on the
order of a few oersteds causes a sharp decrease in resistance of
approximately 90%.  The process requires the fabrication of
sub-micrometer-wide wire of aluminum which has two current leads and
two voltage leads of the same width spaced at a distance of 1
micrometer, as shown in Fig. 1.  Fabrication of the lines utilizes
electron beam lithography and "lift-off" processing.  The metal wire
has a thickness on the order of 35...