We report measurements of the dectrical resistivity, Hall coefficient, magnetoresistance, thermoelectric power, infrared reflectivity, and c-axis lattice parameter of single crystals of titanium disulfide Ti&+"S& with varying degrees of nonstoichiometry. The strong correlations we find between different measurements made on the same sample allow us to conclude that titanium disulfide is a semiconductor rather than a semimetal. Even though this fact is established, our most stoichiometric samples continue to exhibit metallic behavior, and the source of these conduction electrons is unknown. In addition, none of the scattering mechanisms examined here is capable of explaining the unusual temperature dependence of the electrical resistivity which varies as T' at low T and as T~a bove 100 K where y ranges from 1.85 for the least stoichiometric samples to 2.2 for the most stoichiometric.
In the pitch step experiment subjects tune an oscillator in three successive adjustments to match the pitch of a 15-msec sine-wave tone of frequency f2 that is immediately preceded by a 4-sec sine-wave tone with frequency f1 (900 <f1 < 1000 Hz) of the same intensity (82 dB). We find that for upward steps (f2 >f1) the matched tone frequency p2 tends to be greater than f2. This effect, whereby the pitch of tone 1 repels the pitch of tone 2 increases for decreasing |f2−f1|. The effect is reminiscent of the repulsion of a tone by a narrow noise band. [J. C. Webster and D. R. Muerdter, J. Acoust. Soc. Am. 37, 382–383 (1965)]. Therefore, a plot of p2−f1 versus f2−f1 is nonlinear (and possibly discontinuous) near the origin. If p2 is regarded as a description of the state of a pitch perceptor 15 msec after the step then the nonlinearity guarantees that no linear differential equation can describe the time-dependent response of the pitch perceptor. Dichotic experiments with tones 1 and 2 in different ears suggest that a repulsive-type nonlinearity is still present, though reduced in size. For downward pitch steps two of our subjects exhibit a repulsive effect (p2 <f2) and two subjects produce anomalously high p2 tunings.
The thermopowers of single crystals of Cd and W have been measured between 1.5 and 4 K in a magnetic field, directed along high symmetry axes. Care has to be taken in the elimination of probe misalignment effects. The thermopower results are consistent with experimental values for electrical and thermal resistivity tensor elements which occur in the equation for the thermopower in a high magnetic field. However, the apparent departure from the expected field dependence of pxy has led us to question current theory.
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