Kondo effect in mesoscopic systems
Abstract
We have studied the interplay between local moment physics and mesoscopic physics by studying the resistivity of thin metal films containing dilute concentriations of magnetic impurities. Local moments in a bulk metal give rise to an anomaly in the low temperature resistivity known as the Kondo effect. We find that when these materials are fabricated as thin films, the size of the Kondo contribution to the resistivity, ΔρK, depends on several factors related to film geometry, disorder, and spin of the local moment. We have studied films of Cu and Au containing dilute concentrations of either Mn or Fe impurities. For films of Cu(Fe), Δρ K decreases as the film thickness is reduced, but for Cu(Mn) Δρ K remains constant over the same range of film thickness. In addition, we find the suppression of ΔρK depends on the local moment proximity to the film surface, and that a rougher substrate surface results in a greater suppression. In related experiments, it is observed that enhanced film disorder results in a suppression of Δρ K, with this suppression eventually saturating at very low mean free path. The results are compared to previous experimental studies of Cu and Au films containing dilute concentrations of Fe impurities, and to recent theoretical predictions which consider the role of reduced dimensionality and disorder on the Kondo effect.
Degree
Ph.D.
Advisors
Giordano, Purdue University.
Subject Area
Condensation
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