| The scattering of conduction electrons by magnetic impurities is known as the Kondo effect. In metals, the resistivity normally decreases monotonically with decreasing temperature and reaches a constant residual value at zero temperature. In some cases, a minimum was observed in the resistivity at low temperature. This minimum was attributed to the presence of dilute magnetic impurities in the metal host. In this thesis, we discuss the effect of scattering of conduction electrons by Fe magnetic impurities in AgFe Kondo wires.; In a metal containing a small amount of magnetic impurities, the resistivity is proportional to the total scattering rate, which increases with decreasing temperature and then saturates at very low T, where the inelastic scattering events are frozen out. The inelastic scattering rate, t-1f , is important for dephasing of electrons, which is important in quantum transport and mesoscopic physics. Until very recently, there was neither experimental data nor theoretical expression to describe the temperature dependence of the inelastic scattering rate, due to dilute magnetic impurities, valid for temperatures T not too far below the Kondo temperature, TK. In this work, our goal is to measure the magnetic inelastic scattering rate over a broad range of temperature, and to stimulate theoretical work in this direction.; In metals, the conduction electron can be scattered in two ways, elastically or inelastically. It is well known that elastic scattering preserves the phase coherence, since there is no energy exchange between the conduction electron and the scattering center. On the other hand, the inelastic scattering destroys the phase coherence of the conduction electron. At low temperature, there are three main sources for the inelastic scattering in metals; the electron-electron, electron-phonon, and electron-magnetic impurity interactions.; The weak localization magnetoresistance (MR) method is used to determine the value of the electron dephasing time tau&phis;. We have measured tau &phis; for both types of samples, pure and implanted samples. By subtracting the total dephasing rate of the pure sample from the total dephasing rate of the implanted ones, we extract the magnetic scattering rate, gamma m, of the conduction electrons off Fe impurities. We then compare our data with a recent theory of electron dephasing by dilute magnetic impurities.; The high field magnetoresistance is used in this work to obtain an independent estimate of the Kondo temperature, TK. At an intermediate field scale, the implanted samples show a negative MR, whereas in pure films it is positive and proportional to B2. The negative MR observed in the implanted samples is due to the presence of Fe magnetic impurities. From the high field MR data, we find that below 200 mK the magnetoresistivity saturates towards its unitary limit (its value at T = 0), indicating that the Fe spin is completely screened by the surrounding conduction electrons. We then compare our high field data with the Numerical Renormalization Group calculations of the MR for spin 1/2 magnetic impurities, provided to us by Theo Costi. |
