Permeability and Ferromagnetic Resonance Study for Magnetic Nanowires Substrate With Copper Layer

In this letter, a straightforward accurate method for magnetic nanowires (MNWs) ferromagnetic resonance (FMR) frequency determination and permeability extraction is proposed. FMR frequencies are obtained using a one-port coplanar waveguide (CPW) circuit system. Relative permeability, defined as μ = μ'-jμ'', of MNW samples is extracted by “four steps” method, commonly used for thin films (Bekker et al., 2004; Liu et al., 2005; Wei et al., 2015). MNW samples with and without copper (Cu) layer are compared. Samples with a Cu layer show stronger FMR resonances, negligible influences from board resonances, and low distortion μ' compared to those without a Cu layer. From μ'', the average linewidth of a cobalt sample with and without Cu layer is 4.96 and 5.6 GHz, respectively. From the peak of μ'', the FMR frequency of an iron sample is higher at low dc field when compared to cobalt. This can be beneficial for microwave device design when external dc field is limited, and higher operating frequency is required.