Magnetooptical studies of defects and recombination luminescence in LiBaF3

Abstract

Optically detected EPR investigations have been performed on the recombination luminescence (RL-EPR) of LiBaF3 crystal, X-irradiated at T=4.2K. RL-EPR lines of VK- centres were found, as well as further lines of a defect with S=12 and an axial g-tensor with its main axis along a [100] direction of the crystal.Measurements of the magnetic circular dichroism of the absorption (MCDA) have been performed on LiBaF3 crystals X-irradiated at two temperatures (4.2K and RT). After irradiation at T=4.2K, the main MCDA bands peak at 453 and 500nm, but after irradiation at T=300K, the main bands peak at 444 and 390nm, there is a change of the sign between the peaks in both cases. The MCDA-detected EPR (MCDA-EPR) consists of one broad EPR line in both cases and belong to electron trap centres. Analysis of half-widths of MCDA-EPR lines showed that both defects should have g-tensors with their axes along the [100] direction. This symmetry has to be expected for F-type centres in LiBaF3 crystals. The low-temperature electron centre has a more perturbed ground state as the RT centre.