OPTICAL, ELECTRICAL AND MAGNETIC PROPERTIES OF CHALCOPYRITE, CuFeS2

Various optical, electrical and magnetic properties of a magnetic semiconductor, CuFeS2, have been studied. Optical absorption spectra show the absorption edge at 0.6 eV for CuFeSz and strong absorption bands at 1.3 eV and 2.0 eV for Fe-doped CuAIS2. Photoconductivity is also observed at the same energy region of the absorption edge. These strong absorptions originate from the charge transfer transitions relating to 3d orbitals of Fe and the absorption edge of CuFeSz rises from the band-to-band transition corresponding to this charge transfer transition. For nand p-type CuFeS2 electrical conductivities increase slightly with decreasing temperature and carrier concentrations do not depend on temperature. Mobility has small value as 10 cm21V.s for n-type specimen and l cm2/V. S for p-type. Magnetic susceptibility is also temperature independent between 40 K and 600 K and its magnitude is 1 0 3 per mol. These apparent metallic behaviors of electric and magnetic properties are understood from a model of a degenerate semiconductor where 3d orbitals arc appreciably admixed with s and p orbitals and compose both the conduction and valence band.