X-ray near-edge structure of the II-VI compounds containing manganese: Experimental and theoretical studies of Cd1-xMnxTe and Zn1-xMnxTe.

Abstract

Experimental studies of x-ray-absorption edges have been carried out in ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te with x=0.21, 0.52, and 0.7 and in ${\mathrm{Zn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te with x=0.5 for the L edges of Cd and Te and the K edges of Zn and Mn. A comparison is made for ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te with x=0.25, 0.5, and 0.75 and ${\mathrm{Zn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te with x=0.5 with calculated results from electron densities of states in the conduction band obtained from band-structure calculations of the ferromagnetic phases of these materials using the linear muffin-tin orbital method. At these concentrations, band structures and densities of states can be obtained for tetrahedral (x=0.5) and cubic (x=0.25 and 0.75) lattices. The agreement between the experimental and theoretical results for absorption edges calculated using the one-particle approximation is, in general, satisfactory. The validity of the virtual-crystal model for the ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te and ${\mathrm{Zn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te ternary compounds is investigated in terms of both the experimental and theoretical data. From the above experimental data, values for Te ${\mathit{L}}_{1}$ and ${\mathit{L}}_{3}$ x-ray-absorption edges for a hypothetical zinc-blende-structure MnTe (ZB MnTe) have been extracted and compared with the theoretical result. The agreement between the extracted-edge results and the direct theoretical calculation is quite good. Looking at the Te L edges of extracted ZB MnTe, the maximum contributions of the hybridized unoccupied Mn 3d states in ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te and ${\mathrm{Zn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te have been estimated at about 3.8 and 3.0 eV above the conduction-band minimum for p-projected and s,d-projected density of states, respectively.