Systematic errors in the determination of the spectroscopic g factor in broadband ferromagnetic resonance spectroscopy: A proposed solution
A theoretical and experimental study of the influence of small offsets of the magnetic field (dH) on the measurement accuracy of the spectroscopic g factor (g) and saturation magnetization (Ms) obtained by broadband ferromagnetic resonance (FMR) measurements is presented. The random nature of dH generates systematic and opposite sign deviations of the values of g and Ms with respect to their true values. A dH on the order of a few Oe leads to a ~10% error of g and Ms for a typical range of frequencies employed in broadband FMR experiments. We propose a simple experimental methodology to significantly minimize the effect of dH on the fitted values of g and Ms, eliminating their apparent dependence in the range of frequencies employed. Our method was successfully tested using broadband FMR measurements on a 5 nm thick Ni80Fe20 film for frequencies ranging between 3 and 17 GHz.