Dynamic Site-Occupancy Evolution and Defect Engineering in {Tb3}[Ga x Sc1– x ]2(Al3)O12 Magneto-optical Crystals

Abstract

Tb3Sc2Al3O12 is a highly promising magneto-optical crystal for Faraday isolators in high-power solid-state lasers, yet its application is severely restricted by cracking induced by intrinsic lattice distortion and AlSc antisite defects. To overcome these limitations, we adopted a site-selective engineering strategy by growing a series of {Tb3}[GaxSc1–x]2(Al3)O12 crystals to systematically investigate the correlation between Ga3+ occupancy and macroscopic performance. Results demonstrate that Ga3+ ions preferentially eliminate octahedral AlSc antisite defects at low substitution levels. Specifically, the x = 0.25 composition achieves optimal structural integrity and a maximum extinction ratio of 33.7 dB. At this substitution level, Ga3+ precisely eliminates the misplaced octahedral Al3+, effectively releasing internal lattice strain and minimizing microscopic scattering centers while avoiding the compositional disorder associated with excessive doping. Comprehensive evaluation confirms that the x = 0.25 composition offers the best balance of high magneto-optical properties, low scattering loss, and lattice stability. This study provides a rational approach for the compositional design of high-performance garnet crystals for high-power laser applications.