DEGREE OF P-D HYBRIDIZATION IN ZN1-XMNXY (Y=S,SE) AND ZN1-XCOXS ALLOYS AS STUDIED BY X-RAY-ABSORPTION SPECTROSCOPY

We have measured x-ray-absorption near-edge-structure (XANES) spectra of the diluted magnetic semiconductors Zn1-xMnxY (Y = S,Se) and Zn1-xC oxS alloys at the Mn and Co L(3,2) edge. Analysis of the Mn L(3,2)-edg e XANES spectra for Zn1-xMnxY and Co L(3,2)-edge spectra for Zn1-xCoxS revealed the presence of a white-line feature in each series, whose i ntensity increased linearly with concentration x. The white-line featu re is assigned to Mn(Co) 2p(3/2) and 2p(1/2) photoelectron excitations to nonbonding 3d(e) states and to the relatively broadened band of Mn (Co) 3d(t(2))-S 3p hybridized antibonding states for the sulfides, an d to Mn 3d(t(2))-Se 4p hybridized states for the selenides. The rate o f increase of L(3,2) white-line intensity with x is associated with th e 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( t(2))-anion p hybridization is strongest for Zn1-xCoxS, intermediate f or Zn1-xMnxS and least for Zn1-xMnxSe. From separate and Co K-edge ext ended x-ray-absorption fine-structure measurements on Zn1-xMnxS and Zn 1-xCoxS at 77 K, we found that the nearest-neighbor (NN) Mn-S (2.42 An gstrom) and Co-S (2.30 Angstrom) bond lengths remained essentially con stant with x in these alloys, respectively. The degree of relaxation o f the NN Mn (Co)-anion bond lengths is found to be directly related to the strength of p-d hybridization coupling in these alloys.