Photo-Magnetoresistance of Strontium Titanate

抄録

The photo-magnetoresistance of pure SrTiO₃ single crystals was measured by dc method mainly at 10°K. The magnitude of the photo-magnetoresistance is greater by a factor of 5 than that of the magnetoresistance which was observed in the reduced or doped samples. The reduction of the magnetoresistance in the latter samples is due to degeneracy of carriers. From the photo-magnetoresistance for various directions of current and magnetic field the conduction band of SrTiO₃ is deduced to have six equivalent energy minima along the ⟨100⟩ directions in the Brillouin zone. The Photo-magnetoresistance effect at low temperatures can not strictly be described in terms of three coefficients by Pearson and Suhl’s equation for cubic crystals. The results of the piezoresistance measurements, which was considered to be an evidence for a conduction band with the lowest-energy minimum at k=0, can be explained on the conduction band with the lowest-energy minima along the ⟨100⟩ directions.