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Browse Prior Art Database

Ultrasmall Light to Magnetic Field Transducer

IP.com Disclosure Number: IPCOM000116612D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Allenspach, R: AUTHOR [+4]

Abstract

A tricrystal loop can be built of a non s-wave superconductor, which will create a magnetic flux of a half flux quantum threading the ring (1). The magnetic flux is caused by a spontaneously generated circular electric current, which circles the ring in thermal equilibrium. For an s-wave superconductor the electrical current can be generated by means of an external source and appropriate wiring. The inner diameter d sub i and the width w of the ring are typically in the range of 10 micrometer. The device functions for almost any shape of the superconducting film, also in the extreme case that its inner diameter is zero.

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Ultrasmall Light to Magnetic Field Transducer

      A tricrystal loop can be built of a non s-wave superconductor,
which will create a magnetic flux of a half flux quantum threading
the ring (1).  The magnetic flux is caused by a spontaneously
generated circular electric current, which circles the ring in
thermal equilibrium.  For an s-wave superconductor the electrical
current can be generated by means of an external source and
appropriate wiring.  The inner diameter  d sub i  and the width  w of
the ring are typically in the range of 10 micrometer.  The device
functions for almost any shape of the superconducting film, also in
the extreme case that its inner diameter is zero.

      This invention is based on the observation that the magnetic
field in the ring can be turned off and on fatiguelessly by simply
opening and closing the superconducting path of the circular current.
This can be done, for example, by opening or closing a miniaturized
switch incorporated into the ring, or by heating a fraction of the
ring above its superconducting transition temperature Tc with a laser
pulse.  Although the flux threading the ring amounts only to  10 sup
-15 Wb , the flux density can be locally enhanced into the Tesla
regime, by means of small dot of a ferromagnetic film placed inside
the ring as shown in the Figure.  The size s of this particle can be
as small as 10-20 nm.  For this purpose, a ferromagnetic particle,
which in zero field is in plane oriented and out of plane if the flux
is present, can be utilized.  Examples are Fe, Ni, Co, metglass or
permalloy.  If such a ring is heated at one spot, for example by a
modulated laser beam, th...