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 T 2p 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 T 3d states lie near the top of the O 2p valence bands. Only ferromagnetic Zn1-xTxO shows a significantly large Fe 3d photoemission intensity near E-F, in contrast to the negligible Mn and Co 3d photoemission intensities near E-F in nonferromagnetic Zn1-xTxO (T=Mn, Co), suggesting that the high carrier density is important in determining the ferromagnetic behavior of Zn1-xTxO. (C) 2006 American Institute of Physics.