Multilayering FeGa with NiFe and Al₂O₃ to enhance the soft magnetic properties

In this study, the impact of insulating Al2O3 interlayers on the static and dynamic magnetic properties of FeGa/NiFe multilayers was investigated. A multilayer structure consisting of ten (10 nm FeGa)/(2.5 nm NiFe) bilayers was first established to show a reduction in coercivity and high frequency losses compared to a single (100 nm FeGa)/(2.5 nm NiFe) bilayer, which itself shows better performance than a single 100 nm FeGa film. By strategically placing 2.5 nm Al2O3 interlayers in the FeGa/NiFe multilayers (after the FeGa layer but before the next NiFe layer), the composite displayed a reduced coercivity down to 3 Oe while retaining a strong uniaxial anisotropy. Due to the effectiveness of these ultra-thin Al2O3 layers in reducing the eddy current losses across the FeGa/NiFe multilayer stack, this multilayer structure exhibited excellent performance at high frequency, including a gilbert damping coefficient of 0.0081 and an inhomogeneous linewidth of 38 Oe. These results demonstrate that Al2O3 interlayers can improve the soft magnetic properties of (FeGa/NiFe)-based multilayers to enable integration in magnetoelastic and high frequency applications.