Influence of Antisite Defects in Yttrium-Aluminum Garnet on Paramagnetic Centers of Ce³⁺ and Tb³⁺

In yttrium aluminum garnet (YAG) crystals containing terbium and cerium impurities, along with the main EPR signals of Tb3+ and Ce3+ ions located in the dodecahedral sites of the YAG lattice in a regular environment, EPR lines with a lower (several percent) intensity were observed. They also belong to the paramagnetic centers of terbium and cerium, but are characterized by slightly altered parameters-the initial level splitting for non-Kramers Tb3+ ions and g-factors for Ce3+ ions. It is shown that the nature of such centers and their number can be explained by the presence of Y-Al antisite defects, i.e. yttrium ions in the octahedral aluminum positions, in the environment of Tb3+ and Ce3+.