Development of a Ferromagnetic Resonance Measurement System Using NanoVNA

Abstract

Ferromagnetic resonance (FMR) is a fundamental technique for probing magnetization dynamics in spintronic and magnetic materials. However, conventional FMR measurements rely on broadband vector network analyzers (VNAs), whose high cost limits accessibility for small laboratories and educational environments. To overcome this barrier, we have developed a compact and low-cost FMR measurement platform - the NanoVNA-FMR system-based on a commercially available NanoVNA. The setup integrates an electromagnet and a coplanar waveguide (CPW) and is fully automated using Python scripts. This enables synchronized magnetic-field sweeping, S-parameter acquisition, and real-time visualization. The system successfully captures clear FMR spectra that exhibit systematic shifts in resonance frequency with increasing magnetic field. The results are in excellent agreement with those obtained using a conventional VNA-based FMR system, confirming the quantitative reliability of the NanoVNA approach. Additionally, a 3D-printed sample holder further reduces overall system cost. These results demonstrate that the NanoVNA-FMR system provides a practical, accurate, and accessible alternative for quantitative magnetic characterization and educational applications.

Figures (5)

• Figure 1: (a) Schematic diagram of the NanoVNA-based ferromagnetic resonance (FMR) measurement setup, showing the electromagnet, coplanar waveguide (CPW), DC power supply and NanoVNA connections. (b) Photograph of the CPW and the 3D-printed sample holder used in the experiment.
• Figure 2: Screenshot of the Python-based control interface used during FMR measurements. (a) Reference-processed transmission spectra ($S_{21}$), (b) automatically extracted resonance peak positions at each field, and (c) a color map generated from the measured frequency--field dependence. The program performs automatic magnetic-field sweeping and real-time visualization of the transmission spectra acquired by the NanoVNA.
• Figure 3: Representative differential transmission spectra ($S_{21}$) measured at magnetic fields ranging from 5.0 to 40 mT in steps of 5 mT. Each spectrum exhibits a clear resonance peak that shifts toward higher frequency with increasing field strength, indicating field-dependent ferromagnetic resonance behavior. All spectra are fitted using a Lorentzian function.
• Figure 4: Two-dimensional color map of the FMR absorption intensity as a function of frequency and magnetic field. The resonance band appears as a distinct high-absorption region that shifts continuously with increasing field, providing an intuitive visualization of the FMR dispersion.
• Figure 5: (a) Comparison between the results obtained using the NanoVNA and those measured with a conventional VNA. (b) Enlarged view of the measurement range of the NanoVNA (50 kHz–3 GHz).