We investigate high-field ferromagnetic resonance of superparamagnetic
particles with uniaxial anisotropy, In this case, since the field is
large enough to saturate the magnetization, the thermal orientational
fluctuations of the magnetic moment of the particle are negligible. Th
us, we derive the dynamic susceptibility of the system on the basis of
an independent particle model. High-field ferromagnetic resonance has
been performed on fine cobalt particles, The analysis of the spectra
obtained at different frequencies allows us to estimate the effective
magnetic anisotropy, the gyromagnetic ratio, and the transverse relaxa
tion time. (C) 1998 Elsevier Science B.V. All rights reserved.