Separate Time Dependences of Conductance Quantization in Ferromagnetic Ni Nano-wire

The conductance quantization of Ni Nano-wire was investigated by using break-junction technique. When the width of the nano-wire decreased rapidly, the conductance in remanent magnetization states was observed to be quantized in units of 2e2/h. The unit of quantization switched to e2/h when a magnetic field was applied. When the width of the nano-wire varied slowly, however, quantized conductance plateaus in units of e2/h appeared in the remanent state. Even in this case, the plateaus with ne2/h (n = 2,4,6,...) were observed to be more stable than those with ne2/h (n = 1,3,5,...). The results imply the relevance of the local magnetic domain structrure around the contact, as well as its reconfiguration by the magnetic field, to conductance quantization in ferromagnets.