Abstract
Strong emission bands in the visible region are observed in crystals doped with transition-metal ions under excitation at the band-to-band transitions. We report optical responses of Cr-, Co-, and Ni-doped and present optical models for -doped (, V, Cr, Mn, Co, and Ni) to describe the charge-transfer transitions and the transitions between multiplet levels of electrons, which are observed competitively or coexisting, depending on the number of electrons. While the optical responses of Cr- and Ni-doped are dominated by the multiplet-multiplet transitions, those of Ti- and V-doped are governed by the charge-transfer transitions. The two kinds of transitions coexist in the Mn- and Co-doped . These behaviors are well understood based on the numerical results of unrestricted Hartree-Fock approximation.
- Received 15 March 2007
DOI:https://doi.org/10.1103/PhysRevB.76.075111
©2007 American Physical Society