Tuning magnetic and damping properties of soft ferromagnetic FeGaB thin films for high-frequency applications

Soft magnetic materials are widely used in inductors, transformers, and magnetic sensors. Probing their fundamental properties is therefore crucial to gain insights into improving their static and dynamic magnetic behavior. Herein, we report results on iron-gallium-boron (FeGaB) thin films grown on Si substrate using magnetron co-sputtering. Systematic investigation was carried out to examine the influence of sputtering process parameters on tuning the structure and magnetic properties of FeGaB thin films. By precisely controlling FeGa and B targets’ sputtering power, optimal (Fe_1-yGa_y)_1-xB_x films were realized that exhibit excellent magnetic softness (H_c ∼ 6-11 Oe), and a remarkably low effective Gilbert damping (α_eff ∼ 0.009-0.015). Furthermore, ultrafast magnetization dynamics characterized using time-resolved magneto-optical Kerr effect (TR-MOKE) revealed slow relaxation times of the excited magnetic state in the FeGaB thin films. Collectively, these results confirm that the developed FeGaB thin films have promising high-frequency applications including magnetic sensors.