FIRST DETECTION OF MAGNETIC 4D ATOMS ON THE SURFACE OF NOBLE-METALS

We observe for the first time magnetic 4d surface impurities on the su rface of the noble metals Au and Ag. The noble metal films are covered with 1/100 of a monolayer of the 4d metal. The 4d atoms cause, if the y are magnetic, a dephasing of the conduction electron coherence. The dephasing is measured by weak localization. This method is 100 to 1000 times more sensitive than other presently used experimental methods. We investigated the 4d surface impurities Mo, Nb and Rh. In the case o f Mo the dephasing is of the same order of magnitude as the dephasing by magnetic Fe atoms. In the case of Nb the magnetic character is weak er, and represents probably a Kondo-like system. The magnetic characte r of Rh corresponds to local spin fluctuations.