Magneto‐optical effect of rare‐earth‐rich borate glasses prepared using a levitation technique

The magneto‐optical properties of rare‐earth‐rich borate glasses prepared using a levitation technique were thoroughly investigated. Among the series of rare‐earth borate glasses, Tb 2 O 3 –B 2 O 3 and Dy 2 O 3 –B 2 O 3 glasses displayed remarkably large Faraday effects in the visible region. The Verdet constant of 58Tb 2 O 3 –42B 2 O 3 reached −229 rad/T·m at 633 nm, surpassing the value of commercially available single‐crystalline Tb 3 Ga 5 O 12 . Compositions with a higher rare‐earth oxide content (60 mol%) than that of binary glasses facilitated the successful synthesis of Tb 2 O 3 –Dy 2 O 3 –B 2 O 3 ternary glasses. The Verdet constant linearly increased with increasing Tb 2 O 3 content for the glasses with 40 mol% B 2 O 3 . Results indicate that rare‐earth‐rich borate glasses are promising candidates for magneto‐optical applications in the visible region, and that the types and amounts of rare‐earth ion mainly affect these properties.