NMR-STUDY OF THE DILUTED-MAGNETIC-SEMICONDUCTOR ALLOYS CD1-XFEXTE

The diluted magnetic semiconductor alloys Cd1-xFexTe, with x equal to 0.01, 0.02, 0.03, and 0.05, are studied by Cd-113 and Te-125 static and magic-angle-spinning (MAS) NMR spectroscopy at room temperature. The NMR spectra consist of frequency lines that are shifted by neighboring paramagnetic ions via the transfer hyperfine interaction. Assignments of all lines are suggested and their intensities are correlated to the probabilities of finding iron atoms in well-distinguishable conformational positions with respect to the observed nuclei. These assignments are consistent with a random distribution of magnetic ions in the zinc-blende crystal structure of Cd1-xFexTe. From the shifts, transfer hyperfine interaction constants are evaluated for iron atoms two to five bonds away from the observed nuclei. The dependence of the strengths of these constants on the conformations of the bonds between the interacting ions is discussed. From the MAS-NMR spectra the strength of the dipolar interaction between Cd-113 and its nearest-neighboring Fe2+ is also established. The spin-lattice relaxation times of the different lines in the Cd-113 spectra are also measured. From the experimental results it is concluded that the mechanism governing the relaxation is due to the dipolar interaction.