Electronic Hall Mobility in the Alkaline-Earth Fluorides

The electronic Hall mobility has been measured in additively colored samples of Ca${\mathrm{F}}_2$, Sr${\mathrm{F}}_2$, and Ba${\mathrm{F}}_2$ over the temperature range 160-400 °K by a modified Redfield technique. In all cases the data show a temperature dependence which is much steeper than that predicted by the Feynman-Hellworth-Iddings-Platzman continuum polaron theory. It is suggested that a treatment of polaron transport which specifically considers the discreteness of the lattice may be necessary to fully understand transport in these intermediate-coupling materials.