A Phase Analysis Method for Ferromagnetic Resonance Characterization of Magnetic Nanowires

This paper presents a phase analysis method (PAM) in DC field domain to detect ferromagnetic resonance (FMR) properties of magnetic nanowires. The S-parameter phase is extracted, and a derivative is applied to show FMR frequencies and magnetic moment direction. A comparison between magnitude method and PAM is made. The PAM provides advantages in determining the FMR frequencies for overlapped linewidths. For a two-port coplanar waveguide (CPW) test circuit, the sample placement effect is studied. The phase derivative results show consistent FMR frequencies at DC field of 0.905T for different sample placements. Similarly, three different types of nanowires, iron (Fe), cobalt (Co) and nickel (Ni) are measured and can be easily distinguished. Finally, on a one-port shorted CPW test circuit, the length effect is studied. Two nanowire chips from one sample are diced with the same width but different lengths. When compared, their FMR frequencies possess differences of 0.06T using PAM.