An experimental apparatus capable of measuring voltages in the microvoltregion with an accuracy of ± 5.10^(-9) volts is used to determine thetemperature variation of resistivity and Hall coefficient of three specimensof iodide titanium. These specimens are of comparable purity (room temperatureto liquid helium temperature resistance ratio near 30) and possess a highdegree of preferred orientation. The measurements are made at temperaturesbetween 4.2 and 300°K.
The Hall coefficient is found to depend strongly on temperature andcrystalline texture. At room temperature it has a value of -1.8 x 10^(-11)m^3/coulomb in two specimens, whereas in the third it equals + 1.2.10^(-11)m^3/coulomb. Several factors including impurities, changes in the scatteringmechanism, size effects, crystallographic anisotropy, which could account forthe observed differences, are discussed and it is proposed that crystallographicorientation is the most influential factor. From the measured data and aphenomenological theory of the Hall effect developed in the case of singlecrystals, values of the components of the galvanomagnetic tensor, which replacesthe scalar Hall coefficient of isotropic media, are calculated and discussedin connection with a possible model of the Fermi surface of titanium.
Only tentative conclusions can be drawn from the present experimentalinvestigation and no definite explanation can be offered for the differencein the signs of the two principal galvanomagnetic coefficients. Additionalmeasurements on single crystals and extension of these measurements to highertemperatures, as well as investigations of other properties of titanium(topological measurements in particular) must be made before a more comprehensiveband model of titanium metal can be established.
