Low Gilbert damping in Bi/In-doped YIG thin films with giant Faraday effect

Magnetic films with low Gilbert damping are crucial for magnonic devices, which provide a promising platform for realizing ultralow-energy devices. In this study, low Gilbert damping and coercive field were observed in Bi/In-doped yttrium iron garnet (BiIn:YIG) thin films. The BiIn:YIG (444) films were deposited onto different substrates using pulsed laser deposition. Low coercivity (<1 Oe) with saturation magnetization of 125.09 emu/cc was achieved along the in-plane direction of BiIn:YIG film. The values of Gilbert damping and inhomogeneous broadening of ferromagnetic resonance in BiIn:YIG films were obtained to be as low as 4.05 × 10⁻⁴ and 5.62 Oe, respectively. In addition to low damping, the giant Faraday rotation angles (up to 2.9 × 10⁴ deg/cm) were also observed in the BiIn:YIG film. By modifying the magnetic structure and coupling effect between Bi³⁺ and Fe³⁺ of Bi:YIG, doped In³⁺ plays a key role on variation of the magnetic properties. The low damping and giant Faraday effect made the BiIn:YIG film an appealing candidate for magnonic and magneto-optical devices.