N. Giordano et Tm. Jacobs, Substrate dependence of Kondo and local moment physics in thin metal films(invited), J APPL PHYS, 87(9), 2000, pp. 6079-6082
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].