Quantized conductance through iron point contacts

Atomic-size contacts of iron were made in a scanning tunneling microscope (STM) at 4.2 K, and their electronic conduction was studied. We measured the conductance of the contact between the metal substrate and the STM tip as a function of the displacement between them. The observed conductance curves were quantized, and some steps in the conductance curves have hysteresis for repeated displacements. The unit of the quantization is e2/h as expected in ferromagnetic materials without spin degeneracy. We also measured the magnetic field dependence of the conductance up to 150 mT. These results are discussed in terms of the ballistic transport in metallic wires accompanied with the continuous deformation, the sudden atomic rearrangements and the change of the magnetic states around the wires.