The complex permittivity and permeability of superparamagnetic iron-oxide nanoparticles
has been quantified using a circular waveguide assembly with a static magnetic field to align
the nanoparticle's magnetization. The high sensitivity of the measurement provides the
precise resonant feature of nanoparticles. The complex permeability in the vicinity of
ferromagnetic resonance is in agreement with the nanoparticle's measured magnetization
via conventional magnetometry. A rigorous and self-consistent measure of complex …