2e 2 /h to e2/h switching of quantum conductance associated with a change in nanoscale ferromagnetic domain structure

Abstract

We demonstrate the electrical conductance quantization in a Ni nanowire formed in a break junction between a ferromagnetic Ni wire and a Ni plate in applied magnetic fields. The conductance of the nanowire is clearly quantized in units of ${\text{2e}}^2\mathrm{/h}$ in a zero magnetic field, but it is switched to $e^2\mathrm{/h}$ by applying magnetic fields above 60 Oe. This switching behavior seems closely related to a ferromagnetic domain formation in the vicinity of a nanowire, suggesting that nanoscale magnetic domain walls play an important role in determining nanoscale spin-dependent transport. The effect offers the possibility of a new device, a nanoscale colossal magnetoresistive sensor.