Giant Faraday rotation in neon implanted yttrium iron garnet films

The saturation magnetization M
s
and the Faraday rotation θ
F
at λ = 633 nm of yttrium iron garnet films implanted with neon ions of different energies and dosage levels have been investigated as a function of temperature and annealing. The Faraday rotation of the implanted part of the film θ
F
(i) reveals a strong increase in particular for
T \leq 400
K. The annealing of these a further increase of θ
F
(i) reaching value a at T = 4.2K which is more than 10 times the value of the nonimplanted as-grown film. These high θ
F
(i) values are still present after annealing at temperatures where M
s
already approaches the value of the nonimplanted as-grown film. These results can be explained assuming the relative change of the magneto-optical properties by the implantation to be different at octahedral and tetrahedral sites, which leads to a positive contribution of both sublattices to θ
F
(i) essentially via the change of the magneto-optical coefficients.