Files in this item



application/pdf1966_asik.pdf (5MB)Restricted to U of Illinois


Title:Spin-flip scattering of conduction electrons from impurities
Author(s):Asik, Joseph Richard
Doctoral Committee Chair(s):Slichter, C.P.
Department / Program:Physics
Subject(s):spin-flip scattering
conduction electrons
electrons from impurities
spin orientation lifetime
non-magnetic elemental impurities
conduction electron spin resonance (CESR)
Abstract:We report and analyze the results of a new type of experiment, the effect of impurities on the spin orientation lifetime of conduction electrons. We have made a theoretical and experimental study of the effect of non-magnetic elemental impurities on the conduction electron spin resonance (CESR) in metals. By measuring the concentration dependence of the C~SR linewidth, we have obtained the spin-flip scattering cross-sections of 14 different impurities in Li and 7 impurities ,in Na. The mechanism of spin-flip , " is proved to be the spin-orbit interaction of a conduction electron in the electric field of the impurity atom. The smallest crosssection observed is 6 .4 x 10- 21 cm 2 for LiMg while the largest is 2.7 x 10- 16 cm 2 for ~Tl. The range of 105 in order of magnitude is related to the large range in the spin-orbit splittings of the free impurity atoms. We can account for most of the cross-sections by a simple theory which considers as a perturbation the interaction of the conduction electron spin with its orbital motion in the -J,. electric field of the impurity (spin-orbit coupling). Since the spin-orbit interaction occurs well inside the ion core of the impurity, these measurements provide information about the t > 0 terms of the conduction electron wave function in the vicinity of the impurity nucleus. For monovalent impurities we have developed a simple OPW theory which relates the cross-sections to the spin-orbit splittings of the atomic core states of the impurity and to overlap integrals between plane waves and core functions. This theory gives excellent agreement for ~g, ~u, and ~u. For non-monovalent impurities, the effect of screening is taken into account by solving the problem of a conduction electron in a screened Coulomb potential. The screened Coulomb wave functions resulting from this calculation are then orthogonalized to the ,core functions. Excellent agreement is obtained for impurities having valences close to 1. The crosssections for the Group III impurities (In,Tl) and especially the Group IV impurities (Sn,Pb) are anomalously smaller than the theory predicts. In an attempt to resolve this discrepancy we have developed a phase shift formulation of the spin-flip scattering problem in the j,t representation. A formula for the spin-flip cross-section is'found. We also derive a new Friedel sum rule which the j, t phase shifts must satisfy for a spin-dependent interaction of the spin-orbit type. The results of this calculation are not in significantly better agreement with experiment.
Issue Date:1966
Genre:Dissertation / Thesis
Rights Information:1966 Joseph Richard Asik
Date Available in IDEALS:2011-05-20
Identifier in Online Catalog:6174949

This item appears in the following Collection(s)

Item Statistics