Light and spins in rare-earth doped garnets

Abstract

Spin-dependent optical properties of garnet crystals and garnet based ceramics, doped with cerium and also, along with cerium, co-doped with gadolinium and/or terbium, were studied by the method of optically detected of magnetic resonance by monitoring luminescence. The intensity of photoluminescence excited by circularly polarized light in the absorption bands of Ce3+ proved to be useful for selective monitoring of the population of the spin sublevels of the Ce3+ ground state. It was shown that due to cross-relaxation between the cerium and gadolinium electron spin systems the intensity of Ce3+ emission can be used to detect magnetic resonance of Gd3+. High-frequency EPR allowed finding a family of non-Kramers Tb3+ centers in yttrium aluminum garnet crystals. The influence of the magnetic resonance of Tb3+ on the luminescence of Ce3+ was observed. This suggests a coupling between the Tb3+ and Ce3+ systems, which are promising for coherent information processing. In irradiated crystals and ceramics of cerium-doped gadolinium-gallium garnet, magnetic field stimulation of the recombination of radiation defects was found, that is, it was shown that the energy accumulated during irradiation can be released in an external magnetic field. A huge increase in the afterglow intensity in a magnetic field and magnetic memory effects of magnetic memory were explained by the influence of strong internal magnetic fields on spin-dependent recombination.