2e(2)/h to e(2)/h switching of quantum conductance associated with a change in nanoscale ferromagnetic domain structure

We demonstrate the electrical conductance quantization in a Ni nanowire for med in a break junction between a ferromagnetic Ni wire and a Ni plate in a pplied magnetic fields. The conductance of the nanowire is clearly quantize d in units of 2e(2)/h in a zero magnetic field, but it is switched to e(2)/ h by applying magnetic fields above 60 Oe. This switching behavior seems cl osely related to a ferromagnetic domain formation in the vicinity of a nano wire, suggesting that nanoscale magnetic domain walls play an important rol e in determining nanoscale spin-dependent transport. The effect offers the possibility of a new device, a nanoscale colossal magnetoresistive sensor. (C) 1999 American Institute of Physics. [S0003-6951(99)00537-9].