Magnetoresistance of cubic and monodomain tetragonaln-type strontium titanate

Measurements of the magnetoresistance and calculations of the Seitz coefficients of $n$-type SrTi${\mathrm{O}}_3$ are reported. The experimental results on samples of a Nb-doped crystal ($n=4.3\mathrm{}\times {10}^{18}$ ${\mathrm{cm}}^{-3\mathrm{}}$) in the cubic phase at 120 K show that a many-valley model of the conduction band has to be excluded; calculations based on a warped-band model with two degenerated minima at the $\Gamma$ point and on a fit to the experimentally obtained Seitz coefficients yield constant-energy surfaces, density-of-states masses, and cyclotron masses in very good agreement with theoretical results of Mattheiss. For the first time, the influence of the cubic-to-tetragonal phase transition at 105 K could clearly be observed in magnetoresistance measurements on monodomain samples at temperatures below the phase transition.