Optical and EPR spectroscopy of a [La.sub.3][Ga.sub.5]Si[O.sub.14]:Mn crystal

The absorption, circular dichroism, luminescence, and EPR spectra of a [La.sub.3][Ga.sub.5]Si[O.sub.14]:Mn crystal are investigated. Optical measurements are taken at T = 8 and 300 K; EPR spectra are measured at 300 K. The resultant spectra are analogous to the spectra of octahedral-coordinated [Cr.sup.3+] ions in various crystals. In the luminescence spectra, only the ²[E.sub.g] state is active. Analysis of low-temperature optical spectra reveals bands typical of electron transitions in the [Mn.sup.4+] ions with the 3[d.sup.3] configuration in the octahedral position 1a of the structure. The EPR spectrum is correctly described by a Hamiltonian with spin S = 3/2, taking into account the axial and local rhombic distortions of the oxygen octahedra as well as the hyperfine interaction. The parameters of the spin Hamiltonian and their possible spread due to disorder in the crystal structure are estimated. The spread in the directions of the local triad axes of 1a octahedra is estimated from analysis of the position and width of the line.