The controls of magnetization dynamics and magneto-optic properties in single-crystalline yttrium iron garnet capped by rare-earth dysprosium nano-films

The dynamic magnetization of magnetic materials is of fundamental interest and is essential for various applications in magnetic storage, spin wave and wireless communication areas. Traditionally, rare-earth-doped ferromagnets show an enhancement of the Gilbert damping parameter due to the slow relaxation of the 4f-electron spins of rare-earth atoms. The exchange coupling between a ferromagnetic garnet thin film and a nanometer rareearth thin film has been rarely explored. In this work, we fabricated and systematically studied microstructural, static and dynamic magnetic properties of yttrium iron garnet (YIG)/dysprosium (Dy) heterojunctions. Large modulations of the out-of-plane magnetic anisotropy field, Gilbert damping parameter and magneto-optic Kerr rotation angle have been realized in single-crystalline YIG thin films capped by rare-earth Dy nano-films. Both the effective Gilbert damping parameter, alpha(eff), and the Kerr rotation angle, increase by 300% for the YIG/Dy(60 nm) heterostruture compared to the bare YIG ferromagnet. The enhanced alpha(eff) strongly depends on the out-of-plane magnetic anisotropy field, which arises from the interfacial exchange coupling between YIG and Dy nano-films. Our findings provide a robust route to control both magnetization dynamics and magneto-optic properties using rare-earth nano-films.