Magnetically induced circular emission of Cr(III): MgO

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Abstract
We report the emission spectrum and magnetically induced circular emission, MCE, from Cr3+ ions in MgO. The principal sharp line features are the well-known emissions from undistorted Cr3+ sites and from Cr3+ sites associated with lattice vacancies which provide a tetragonally distorted environment. Of the weaker lines, we find evidence which suggests that the feature at 14 216 cm-1 is associated with a non-collinear Cr3+-vacancy-Cr3+ system. Also our results suggest that the features at 14 115 and 14 123 cm-1 are due to emission from Cr3+ perturbed by Mg2+ in an orthorhombic position and Cr3+-vacancy-Cr3+ in the orthorhombic direction. The phonon structure in the MCE suggests a strong contribution from a t 2u ‘cluster’ mode in agreement with the calculation of Sangster. Emission spectra are reported using the chronospectroscopic technique to display the 2 Eg and 4 T 2g bands separately. The spectrum from the 4 T 2g state exhibits some previously unobserved sharp features which may originate from the different Cr3+ sites in the lattice.
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