  The phenomenon of ferromagnetic resonance (FMR) is still being exploited for
determining the magnetocrystalline anisotropy constants of magnetic materials.
We show that one can also determine accurately the saturation magnetization of
the sample using results of FMR experiments after taking into account the
relationship between resonance frequency and curvature of the spatial
distribution of free energy at resonance. Specifically, three examples are
given of calculating saturation magnetization from FMR data: we use historical
Bickford's measurements from 1950 for bulk magnetite, Liu's measurements from
2007 for a 500 mn thin film of a weak ferromagnet (Ga, Mn)As, and Wang's
measurements from 2014 for an ultrathin film of YIG. In all three cases, the
magnetization values we have determined are consistent with the results of
measurements.
