  We have observed a super-giant (~10,000,000%) negative magnetoresistance at
39 mT field in Cu nanowires contacted with Au contact pads. In these nanowires,
potential barriers form at the two Cu/Au interfaces because of Cu oxidation
that results in an ultrathin copper oxide layer forming between Cu and Au.
Current flows when electrons tunnel through, and/or thermionically emit over,
these barriers. A magnetic field applied transverse to the direction of current
flow along the wire deflects electrons toward one edge of the wire because of
the Lorentz force, causing electron accumulation at that edge and depletion at
the other. This lowers the potential barrier at the accumulated edge and raises
it at the depleted edge, causing a super-giant magnetoresistance at room
temperature.
