Quantized Conductance of a Single Magnetic Atom

A single Co atom adsorbed on Cu(111) or on ferromagnetic Co islands is contacted with nonmagnetic W or ferromagnetic Ni tips in a scanning tunneling microscope. When the Co atom bridges two nonmagnetic electrodes a conductance of approximate to 2e(2)/h is found. With two ferromagnetic electrodes a conductance of approximate to e(2)/h is observed.