Investigation of the phase separations and the local electronic structures of Zn1−xTxO (T=Mn, Fe, Co) magnetic semiconductors using synchrotron radiation

The spatial chemical distributions of doped T ions and their local electronic structures in Zn1−xTxO (T=Mn, Fe, Co; x⩽0.1) have been investigated simultaneously by using scanning photoelectron microscopy (SPEM), photoemission spectroscopy (PES), and soft-x-ray absorption spectroscopy (XAS). The measured SPEM images for Zn1−xTxO single crystals reveal the uniform chemical distributions of T ions, indicating the homogeneous substitution of T ions for Zn sites. The T2p XAS spectra of Zn1−xTxO show that Mn and Co ions are in the divalent states, while Fe ions are in the Fe2+–Fe3+ mixed-valent states. The valence-band PES study of Zn1−xTxO (T=Mn, Fe, Co) shows that T3d states lie near the top of the O 2p valence bands. Only ferromagnetic Zn1−xTxO shows a significantly large Fe 3d photoemission intensity near EF, in contrast to the negligible Mn and Co 3d photoemission intensities near EF in nonferromagnetic Zn1−xTxO (T=Mn, Co), suggesting that the high carrier density is important in determining the ferromagne...