Quantized conductance through atomic-sized iron contacts at 4.2 K

We studied the conductance of atomic-sized wires of iron made in a scanning tunneling microscope (STM) at 4.2 K, The conductance was measured as a fun ction of the displacement between the iron substrate and the STM tip during the elongation and compression of the wires. The observed conductance curv es were quantized, and some of the steps in the conductance curves display hysteresis for repeated displacements. The unit of the quantization is e(2) /h as expected in ferromagnetic materials. A magnetic field of up to 150 mT hardly affects the conductance. These results are discussed in terms of th e ballistic transport accompanied with the sudden atomic rearrangements and the continuous deformation around the wires.