Influence of annealing on magnetization, Faraday rotation, and optical absorption of high-energy heavy ion irradiated garnet films

Y
3
Fe
5
O
12
(YIG) and Gd
3
Fe
5
O
12
(GIG) films have been irradiated with 238U ions of specific energy 1.4 MeV per nucleon. The temperature dependences of the saturation polarization, I
s
, and of the Faraday rotation Θ
F
(λ = 633 nm), and at T = 293 K the spectra of the Faraday rotation and of the optical absorption of the YIG films were measured after various annealing treatments. Annealing of films damaged by ion irradiation leads to an increase of the Faraday rotation of YIG and GIG. In YIG a 4.3 times higher value than in the as-grown film can be created at low temperatures. This strong Θ
F
enhancement is attributed to a line broadening of the optical transitions.