Conduction band symmetry and spin-dependent polaron transport in the alkali halides

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Abstract
The transverse magnetoconductivity of photo-excited electrons in KCl, KBr, KI, NaI and RbCl has been studied at low temperatures as a function of the orientation of the magnetic field with respect to the crystal axes. The minimum of the lowest conduction band in these substances is found to be highly isotropic. The first studies are reported of the dependence on the orientation of the conduction electron spins of electronic transport in alkali halide crystals containing F centres. These measurements can be understood in terms of the interaction of spin polarized conduction electron with spin polarized F centres. It appears that the transport of photoelectrons at 4.2 degrees K in KCl, KBr and KI containing 1016 to 1017 F centres per cm3 occurs by a diffusive motion as in conventional transport theory and that a spin-dependent scattering or trapping time may be defined.