Micromagnetic study on micro-structured ferromagnetic thin film for high-frequency-device applications

Various effects of geometry on the magnetic properties at microwave frequencies (∼ 20 GHz) are systematically studied for micro- and nano-structured ferromagnetic thin films with fourfold in-plane magnetic anisotropy by using micromagnetic simulations. Obtained numerical results on the dynamics of the micro-and the nano-structured magnetic thin film are useful for design considerations for various high-frequency devices, including thin-film inductors, microwave filters and absorbers. The permeability and the resonance frequency are found to be well scaled with a structural parameter of w/t (w = lateral pattern size and t = film thickness) for pattern sizes that differ by an order of magnitude. An exceptional resonance behavior of the smallest pattern with w = 0.5 µm was reasoned to be significant in suppressing the precession in the vicinity of the pattern edge. We also demonstrated that stable magnetization directions orthogonal to each other could be switched with external fields, enabling local control of the permeability in the structured pattern.