Strong Faraday rotation in Ce and Bi comodified epitaxial iron garnet films:Valence control through strain engineering

摘要

The correlation between lattice-misfit strain and the valence change of cerium was investigated in cerium and bismuth comodified iron garnet epitaxial films. We demonstrated that the transition of the valence state from Ce~(4+) to Ce~(3+) is triggered by reducing the compressive lattice-misfit strain and that the increase in concentration of Ce~(3+) induces a red-shift of the optical bandgap as well as an enhancement of the Faraday rotation. An extraordinary Faraday rotation of 0.91 deg/μm at 1.55 μm was achieved in these films by maximizing the concentration of Ce~(3+) through strain engineering.