Substrate dependence of Kondo and local moment physics in thin metal films(invited)

Recent experiments have revealed that Kondo behavior in reduced geometries can be quite different from that found in the corresponding bulk systems. F or example, the Kondo contribution to the resistivity in thin metal films c an be suppressed by reducing the film thickness. This behavior has been exp lained theoretically by Zawadowski and co-workers [O. Ujsaghy, A. Zawadowsk i, and B. L. Gyorffy, Phys. Rev. Lett. 76, 2378 (1996); O. Ujsaghy and A. Z awadowski, Phys. Rev. B 57, 11598 (1998); 57, 11609 (1998)]. in terms of a model involving a surface induced single ion anisotropy at the local moment site. Moments which are near a surface experience a splitting which can re sult in a nonmagnetic ground state. In this article we describe experimenta l observations regarding such surface effects, and in particular the influe nce of the substrate on the Kondo behavior. We find that with substrates of freshly oxidized Si or freshly prepared SiO coated glass, the Kondo effect can be much larger than when the same film is deposited on glass. This fin ding seems to resolve a long standing controversy in the field. (C) 2000 Am erican Institute of Physics. [S0021-8979(00)34008-7].