The production and detection of electron polarization are discussed in the context of low-energy collision phenomena. After a short summary of the history of the subject, the formalism of Stokes parameters is reviewed. Physical processes are surveyed in the following sequence: elastic collisions with spin zero targets (Mott scattering); spin exchange in elastic scattering from spin one-half targets; spin-orbit coupling effects and spin exchange in inelastic electron-atom collisions; photoionization; collisional ionization in atom-atom interactions. The phenomena are described in terms of the algebraic formalism developed in the earlier part of the paper and brief descriptions of experiments illustrate the methods used and the results obtained in testing theoretical predictions. This review was completed in November 1971.

https://iopscience.iop.org/article/10.1088/0034-4885/34/3/305/pdf

Electron spin polarization

In the Stokes parameter formulation of electron and optical polarization, interactions which alter the state of beam polarization are represented by 4*4 transfer matrices. A classification scheme has been introduced for these matrices based on criteria descriptive of their behaviour under unitary similarity transformations. It is shown in particular that nonsingular transfer matrices may be organized in a group which is homomorphic on the Lorentz group and this result allows the polarizing action of a number of dissimilar processes to be described in terms of a simple geometrical picture. The results have been illustrated by a number of examples selected from the field of optics and two forms of electron scattering, which provide the bases of methods for producing polarized electrons, have been analysed in detail.

A classification of electron and optical polarization transfer matrices

When electrons are interacting with a ferromagnetic material, their spin-polarization vector is expected to move. This spin motion, comprising an azimuthal precession and a polar rotation about the magnetization direction of the ferromagnet, has been studied in spin-polarized electron scattering experiments both in transmission and reflection geometry. In this review we show that electron-spin motion can be considered as a new tool to study ferromagnetic films and surfaces and we discuss its application to a number of different problems: (a) the transmission of spin-polarized electrons across ferromagnetic films, (b) the influence of spin-dependent gaps in the electronic band structure on the spin motion in reflection geometry, (c) interference experiments with spin-polarized electrons and (d) the influence of lattice relaxations in ferromagnetic films on the spin motion.

http://iopscience.iop.org/article/10.1088/0953-8984/23/47/473201/pdf

Electron-spin motion: a new tool to study ferromagnetic films and surfaces

When electrons interact with a ferromagnet, their spin polarization vector is expected to move, depending on the magnetization of the ferromagnetic material. This spin motion, consisting of an azimuthal precession and a polar rotation about the magnetization direction, is measured. The precession of the spin polarization vector generates a torque on magnetization that turns out to be large with low-energy electrons. This makes injection as well as reflection of spin-polarized electrons an attractive alternative concept for magnetization switching.

https://www.slac.stanford.edu/pubs/slacpubs/10000/slac-pub-10018.pdf

The Dynamic Response of Magnetization to Hot Spins

Publisher Summary This chapter discusses the real Fermi gas of 3 He that cannot be cooled into the strongly degenerate regime because condensation into the liquid phase comes first 3 He dissolved in superfluid liquid 4 He-II is a fermion system, and if the fraction of 3 He in the solution is less than about 6%, the solute behaves in many ways like a perfect Fermi gas that can be cooled towards the absolute zero of temperature without condensation occurring Fermi degeneracy effects have been experimentally demonstrated in a number of ways Three characteristic lengths could be expected to play parts in determining the properties of a gas of 3 He, whether or not it is polarized These are (1) the mean distance n –1/3 between atoms, where n is the number density, (2) the range a 0 of the interatomic potential, and (3) the de Broglie thermal wavelength It has been shown that the spin diffusion in a partially polarized system is not isotropic, the diffusion of the longitudinal component of the polarization being quite different to that of the transverse component

Chapter 2: Properties of Strongly Spin-Polarised3He GAS

Electron-atom spin exchange collision is described in terms of Stokes parameters. It is shown that if the incident electron beam has a polarization component perpendicular to that of the target then the former is rotated about the direction of the target polarization in a manner analogous to the Faraday rotation of optical polarization. The angle of rotation depends mainly on the phase shift between the triplet and singlet scattering amplitudes. It is pointed out that the electron spin rotation occurring in Mott is analogous to the rotation of the plane of polarization of light by media of natural activity.

J Byrne

Papers

Faraday rotation of electron spin polarization