Effect of crystallization annealing on the formation of double-layer iron garnet films deposited by magnetron sputtering for photonics and integrated optics

Two-step methods for the synthesis of magneto-optical iron garnets with a high bismuth content, based on the growth of a nonthermodynamical garnet with a high bismuth content on a thermodynamic garnet sublayer, have become widely known now. This paper shows how the degree of crystallinity of the garnet sublayer (yttrium iron garnet) affects the formation of the main magneto-optical layer (bismuth-substituted iron garnet). The degree of crystallinity of the sublayer was controlled by changing the time of crystallization annealing of the amorphous layer deposited by the magnetron method. Crystallization of the sublayer occurs through the formation of crystallization centers in the form of circular micron-sized islands. It has been experimentally demonstrated that a high-quality double-layer film with a large specific Faraday rotation of the main magneto-optical layer –27.78°/μm and a homogeneous polycrystalline structure is formed with an annealing duration of the sublayer of 60 min. The synthesized double-layer films in this case demonstrate record low coercivity for those obtained by vacuum sputtering methods, from 67 to 97 Oe. Double-layer films can be effectively used in photonic structures and nanodevices.