Comparison of field sweep and frequency sweep evaluations of Co–Ni ferrite nanoparticles in the short circuit FMR method

Broadband ferromagnetic resonance (BFMR) spectroscopy analysis can be achieved with different setups involving the frequency-sweep and field-sweep setups. To evaluate and compare the two former regimes, a frequency-sweep and a field-sweep shortcut BFMR regimes were conducted on Co–Ni ferrite nanoparticles that were synthesized by the co-precipitation method of metal chlorides. The nanoparticles were structurally and magnetically characterized, with an average particle size of around 23 nm and a spinel structure. The saturation magnetization was about 59 emu/g, and the coercivity was about 30 Oe. The BFMR analyses were achieved through a frequency range of (2–26) GHz and a field range of (0-10⁴)Oe. The two regimes, frequency sweep and field sweep, showed linear behavior between the resonance field and resonance frequency. The frequency–sweep regime displayed more complicated curves involving small multi-peaks within the multi-FMR absorption band that were not found in the field sweep regime. The intercepts of the linear dispersion relationship between the two regimes are nearly equivalent to each other. The field-sweep g-factor was higher and more reasonable than the frequency-sweep one, whereas its damping factor was lower. The fluctuation in the frequency linewidth vs. resonance field in the frequency-sweep method is higher than that for the field-sweep.