Magnetic circularly polarized emission and magnetic circular dichroism of resolved vibronic lines in Cs2GeF6: Mn4+

Publisher Website
Google Scholar
Abstract
Magnetic circularly polarized emission (M.C.P.E.) and magnetic circular dichroism (M.C.D.) techniques have been used to study at low temperatures resolved vibronic lines of the 4 A 2g ↔2 Eg transition in octahedral Mn4+(3d3) in the cubic host Cs2GeF6. Measurements have been made with applied magnetic field (and light propagation) along the [001] (F-Mn-F bond) and [111] directions. Though the Zeeman energy patterns are isotropic, the intensity patterns are not, and U′(Γ8) eigenvectors for arbitrary field orientation have been derived. These have been used to calculate Zeeman intensity patterns for the [001] and [111] crystallographic directions, and the observed intensity variations with orientation are found to provide useful information about intensity mechanisms. In the case of the magnetic dipole origin, the intensity patterns as a function of orientation can be well accounted for by a first-order mechanism which, however, does not predict the small positive M.C.D. observed at the zero-field energy in the [111] orientation. A detailed analysis of this feature and previously measured energy spacings suggest that ζ3d(Mn4+) should have a value of ∼360 cm-1 rather than the value 240 cm-1 usually assumed. Electric dipole vibronic sidebands have been observed corresponding to v 6(t 2u ), v 4(t 1u ), v 3(t 1u ), v 4(t 1u ) + v 5(t 2g ) and v 2(eg ) + v 6(t 2u ). Using a U′→U′ vibronic intensity mechanism with spin-orbit mixing (Appendix A), the M.C.P.E. and total emission patterns for the first two of these regions can be quite well accounted for quantitatively. The corresponding M.C.D. in both cases, while in qualitative agreement with the M.C.P.E., shows much more complicated splitting patterns which are not explicable in terms of a simple k = 0 model. The other three vibronic regions can be accounted for qualitatively. In Appendix B a formula is derived which explicitly relates the M.C.P.E. of a vibronic emission line to its M.C.D. absorption counterpart.