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FAR INFRARED OPTICAL PROPERTIES OF IRON(X)TANTALUM(1-X)DISULFIDE
Abstract
Fe(,x)Ta(,1-x)S(,2), for x (LESSTHEQ) 0.33, is of interest because it shows a large increase in resistivity at low temperatures due to Anderson localization of the conduction electrons by the random potential caused by the iron impurity atoms. To learn more about Fe(,x)Ta(,1-x)S(,2) and localized electrons, far infrared transmission measurements were made between 5 cm('-1) and 350 cm('-1) on this system with x = 0.05, 0.10, 0.20, and 0.33 at liquid helium temperatures. The samples studied had rough surfaces, with the variation in sample thickness being the same order of magnitude as the sample thickness and also as the wavelength of the radiation. Furthermore, the experimental conditions were such that multiple reflections and interference had to be accounted for. Because of this, the standard transmission data reduction could not be performed, so a new data reduction method was developed. The new method consisted of fitting the data to the formula for transmission of radiation through an ideal slab-shaped sample averaged over the distribution of thickness of the real samples, to determine the complex index of refraction. The absorption constant, conductivity, and single surface reflectivity were then determined from the complex index of refraction. It was found for Fe(,x)Ta(,1-x)S(,2) that at frequencies lower than 40 cm('-1) the conductivity agreed with a model for conduction to phonon-assisted hopping between localized states and at higher frequencies other processes had to be considered. The impurity-induced lattice mode absorption was found to be the dominant absorption process at frequencies higher than 40 cm('-1).
Subject Area
Condensation
Recommended Citation
GALLIARDT, DONALD WAYNE, "FAR INFRARED OPTICAL PROPERTIES OF IRON(X)TANTALUM(1-X)DISULFIDE" (1983). ETD collection for University of Nebraska-Lincoln. AAI8314901.
https://digitalcommons.unl.edu/dissertations/AAI8314901