A Ferromagnetic Resonance Measurement System for Small Volume Magnetic Nanowires

Abstract

This work presents a ferromagnetic resonance (FMR) characterization system for magnetic nanowires on short-circuited coplanar waveguide (CPW) structure. The FMR frequency of cobalt (Co) nanowire chips, with three different volumes-small, medium and large, were measured and compared with Kittel equation. The FMR response of the large chip agrees well with Kittel equation with the mean difference of 0.865GHz. The small and medium chips have higher mean difference values of 1.855GHz and 2.205GHz, respectively. From the FMR response, the signal to noise ratio is reduced as the material volume decreased and resulted in less accurate FMR frequency extraction. Since the lowest detectable signal strength of VNA (Anritsu 37369D) is 0.0002, to detect FMR response accurately for this system, the volume of Co should be greater than 2. 2 ×10−4mm3 and the magnetization should be larger than 317µemu. This paper provides a framework for building identification systems such as nanolabels for low volume biosensing application.