The Hall effect, thermoelectric power, and electrical conductivity have been measured as a function of temperature in crystals of $p$-type titanium sesquioxide. A transition is observed at about 450°K. Below this temperature the crystals behave like semiconductors, while above it the conductivity is apparently metallic. The behavior below 450°K is in line with antiferromagnetic ordering. The effective mass of the holes is found to be about $5m_0$ and the average Hall mobility 5 ${\mathrm{cm}}^2$/volt-sec at room temperature. It is claimed that these values, combined with the fact that the Hall effect is measurable, support the assumption of conduction in a narrow $3d$ band.

• Received 31 March 1961

DOI:https://doi.org/10.1103/PhysRev.123.1257