We have measured x-ray-absorption near-edge-structure (XANES) spectra of the diluted magnetic semiconductors (Formula presented)(Formula presented)Y (Y=S, Se) and (Formula presented)(Formula presented)S alloys at the Mn and Co (Formula presented) edge. Analysis of the Mn (Formula presented)-edge XANES spectra for (Formula presented)(Formula presented)Y and Co (Formula presented)-edge spectra for (Formula presented)(Formula presented)S revealed the presence of a white-line feature in each series, whose intensity increased linearly with concentration x. The white-line feature is assigned to Mn(Co) (Formula presented) and (Formula presented)photoelectron excitations to nonbonding 3d(e) states and to the relatively broadened band of Mn (Co) 3d((Formula presented))-S 3p hybridized antibonding states for the sulfides, and to Mn 3d((Formula presented))-Se 4p hybridized states for the selenides. The rate of increase of (Formula presented) white-line intensity with x is associated with the difference in the degree of p-d hybridization of states between Mn (Co) 3d and S 3p for the sulfides, and between Mn 3d and Se 4p for the selenides. Our results indicate that the magnetic-transition-metal 3d((Formula presented))-anion p hybridization is strongest for (Formula presented)(Formula presented)S, intermediate for (Formula presented)(Formula presented)S and least for (Formula presented)(Formula presented)Se. From separate and Co K-edge extended x-ray-absorption fine-structure measurements on (Formula presented)(Formula presented)S and (Formula presented)(Formula presented)S at 77 K, we found that the nearest-neighbor (NN) Mn-S (2.42 Å) and Co-S (2.30 Å) bond lengths remained essentially constant with x in these alloys, respectively. The degree of relaxation of the NN Mn (Co)-anion bond lengths is found to be directly related to the strength of p-d hybridization coupling in these alloys.


Physics, Astronomy, and Materials Science

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© 1997 The American Physical Society

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Physical Review B - Condensed Matter and Materials Physics