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

Abstract

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.