Ferromagnetic Resonance

Ferromagnetic Resonance (FMR) is a powerful technique used to study the magnetic properties of ferromagnetic materials, crucial for applications in spintronics, magnetic storage, and high-frequency devices. FMR measures the precession of magnetization in a material when excited by a microwave field in the presence of an external magnetic field. This precession reveals key properties like magnetization, anisotropy, and damping, providing insights into how materials respond to dynamic magnetic fields. One critical parameter, Gilbert damping, quantifies the energy dissipation rate during precession, influencing the efficiency of magnetic switching and signal transmission.

To measure FMR and extract parameters like Gilbert damping of soft magnetic high entropy alloy e.g. AlxCrFeCoNi, I employed broadband FMR spectroscopy using a vector network analyzer (VNA). The setup involves placing a sample in a magnetic field and applying microwave signals across a wide frequency range (typically GHz to tens of GHz) to excite magnetization precession. The VNA records the absorption spectra, and the linewidth of the resonance peak is analyzed to determine damping. By fitting the linewidth data as a function of frequency using the Kittel equation and Landau-Lifshitz-Gilbert model, the Gilbert damping constant is calculated with high precision. This method, leveraging the VNA’s sensitivity, allows detailed characterization of magnetic dynamics, aiding in the development of advanced magnetic materials.