We examine the radiation induced modification of the Hall effect in high mobility GaAs/AlGaAs devices that exhibit vanishing resistance under microwave excitation. The modification in the Hall effect upon irradiation is characterized by (a) a small reduction in the slope of the Hall resistance curve with respect to the dark value, (b) a periodic reduction in the magnitude of the Hall resistance, Rxy, that correlates with an increase in the diagonal resistance, Rxx, and (c) a Hall resistance correction that disappears as the diagonal resistance vanishes.

We suggest an approach for characterizing the zero-field spin splitting of high mobility 2D electron systems, when beats are not readily observable in the Shubnikov-de Haas effect. The zero-field spin splitting and the effective magnetic field seen in the reference frame of the electron are evaluated from a quantitative study of beats observed in radiation-induced magnetoresistance oscillations

The augmented-plane-wave (APW} method was used to calculate spin-polarized energy bands for body-centered-cubic iron at the normal lattice constant and at lattice spacings corresponding to approximate pressures of 128 and 256 kbar. Both nonrelativistic and semirelativistic energy bands at each pressure were determined with the use of potentials that incorporated the von Barth-Hedin formalism for exchange and correlation. The APW method was used to generate the energy bands at 55 k points of an irreducible wedge in the Brillouin zone; then a Slater-Koster Hamiltonian, fitted to the APW results, was used to generate the energy bands at 1785 k points in the irreducible wedge and to calculate extremal areas of the Fermi surface and their pressure derivatives. To improve agreement with experiment, the first-principles spin-polarized energy bands were rigidly shifted for each lattice spacing by an amount necessary to reproduce the experimental magneton number. The orders of magnitude of the calculated pressure derivatives of the extremal areas were 10 /kbar for the spin-up electron s-d piece,-10 /kbar for the spin-down hole octahedron at symmetry point H, 10 /kbar for the spin-up hole pockets at point H and the electron octahedron at point I, and 10 /kbar for the spin-down electron ball.