Laura M. Roth

Ferrite Phase Shifters in Rectangular Wave Guide

The problem of the propagation of electromagnetic energy down an infinitely long rectangular wave guide partially filled by a ferrite slab is solved. The solution is expressed in the form of a transcendental equation involving the propagation constant. Calculations are carried out for a lossless ferrite, and the phase constant is evaluated as a function of the appropriate parameters, namely, the ferrite slab thickness, the lateral position of the slab in the guide, and the applied transverse static magnetic field intensity. The results are plotted in graphic form for values of the static magnetic field in the region of ferrite saturation both above and below ferromagnetic resonance. The electromagnetic field configurations within the wave guide are plotted in detail for values of the parameters of practical interest. Two versions of the nonreciprocal phase shifter are discussed. The first consists of a single slab placed asymmetrically in the wave guide, while the second consists of two symmetrically plac...

Theory of bloch electrons in a magnetic field

Abstract An effective Hamiltonian is obtained for a Bloch electron in a magnetic field. Using a basis set of modified Bloch functions, a momentum space Schrodinger equation is first obtained, which is formally exact but which has interband terms and also has a normalization matrix differing from the unit matrix. A non-unitary transformation is then used to obtain a one-band Hamiltonian to any order in the magnetic field, and this is carried out to second order for at most two-fold degenerate bands including spin-orbit interaction. The result is applied to obtaining the normal magnetic susceptibility of Bloch electrons.

Oscillatory magneto-absorption in gallium antimonide JA-1149∗☆

Abstract High-resolution magneto-absorption measurements made at photon energies just above the intrinsic absorption edge in GaSb have revealed an oscillatory spectrum having a strong resemblance to the corresponding spectrum for direct transitions in germanium. Eight successive transmission minima were observed in magnetic fields up to 38.9 kG at both 1.5 and 4.2°K, using polarized incident radiation. The value of the energy gap found is g = 0.813±0.001 eV and is shown to be attributable to direct transitions of electrons between the valence and conduction bands. The electron effective mass, m∗ = (0.047 ± 0.003)m0, was determined by considering transitions from the heavy holes to the conduction band and employing the data of the E||B spectrum. The existence of fine structure, although not resolved, is indicated by the unsymmetrical character of some of the transmission minima. The first absorption line is believed to contain exciton absorption. The inability to resolve the fine structure and exciton absorption is attributed to line broadening and overlapping due chiefly to scattering by the high impurity density in the sample.

THEORY OF ELECTRICAL CONDUCTION IN HIGH MAGNETIC FIELDS

Abstract It is pointed out that previous quantum-mechanical theories of transport in high magnetic fields are deficient in that they neglect the effect of the electric field on scattering. It is demonstrated here that in the case of large Hall angles, i.e. ω 0 τ > 1, the transverse current can be obtained by a direct expansion in powers of the scattering potential. Both elastic and inelastic collisions are considered. It is found that the transverse current can be described in terms of the drift of the centers of cyclotron orbits of the electrons in the magnetic field. This justifies the original semi-classical method of calculation of T iteica . It is pointed out, however, that such a procedure is correct only for a non-oscillating electric field. No applications are made.

Quantum magneto-absorption phenomena in semiconductors

Abstract The existence of quantized magnetic or Landau levels in a semiconductor in a magnetic field can give rise to a variety of magneto-absorption phenomena. The oscillatory magneto-absorption of the direct transition has been observed in germanium, indium arsenide and indium antimonide.