ELECTRICAL PROPERTIES OF TI2O3 SINGLE CRYSTALS

Crystals of Ti2O3 of relatively high purity or doped with various impurities have been grown by the Czochralski method. The semiconductor-metal transition commenced at 435°K with a change of resistivity from 9×10-3 to 3×10-4 Ω cm. The resistivity at 4.2°K varies between 0.02 and 6×105 Ω cm, depending on purity and stoichiometry. At 77°K and 273°K, the Hall coefficients are positive, small, and independent of magnetic field. At 4.2°K, reliable values could not be obtained. Magnetoresistance was measured in fields up to 220 kG. At 77°K and above, Δρρ0 never exceeds 10-3. At 4.2°K, Δρρ0 for the purest sample rises quadratically with applied magnetic field, reaching a value of about 4 at 220 kG. This result cannot be interpreted in terms of a one-band model. A method has been developed for determining carrier mobilities from magnetoresistance data for an intrinsic semiconductor with mirror-image bands. Application of this method to the data for the purest samples yields carrier mobilities of 500-1000 cm2/V sec at 4.2°K. The various results have been interpreted in terms of an elementary band-structure model which does not invoke antiferromagnetic ordering effects to explain the semiconductor-semimetal transition observed in Ti2O3. © 1968 The American Physical Society.