A new spectrometric method, using a magneto-optical effect, to study magnetic liquids

Maghemite nanoparticles with very high AC-losses for application in RF-magnetic hyperthermia

“…Refs. [9,10]) at least for Brown relaxation. Since we are interested in the specific loss power we consider only the dependence of the imaginary part of the susceptibility on the external field frequency f to be described according to…”

“…Refs. [9,10]) in studies of Brown relaxation by means of magneto-optical birefringence that in this case the CC data plot may be well approximated by a half circle which corresponds to a susceptibility spectrum of the Debye model. Since magneto-optical effects in ferrofluids are mainly related to the Brownian motion of particles, other relaxation processes (e.g.…”

“…Especially for particle systems with high anisotropy (e.g. CoFe 2 O 4 [9]) Brown relaxation was well investigated while N! eel relaxation is restricted to comparably small particle size in that case.…”

Magneto-optic measurement of Brownian relaxation of magnetic nanoparticles

“…The change of AC susceptibility upon binding to biological target molecules is observed as a decrease of the frequency for the peak of w 00 , which depends on the effective Brownian relaxation time determined by the hydrodynamic size of the nanoparticles. There have been several alternative approaches proposed to measure AC susceptibility using magneto-optical effects (Faraday or CottonMouton effect) [16,17]. These techniques have also been used to detect the binding of biological molecules to magnetic nanoparticles by time-dependent birefringence, which is related to the Brownian relaxation [18].…”

“…The optical anisotropy induced in a suspension of magnetic nanoparticles causes a change in both the eigenmodes of radiation in the medium and in the polarization of linearly polarized incident light upon transmission. When a weak external magnetic field is applied parallel to the wave vector, the polarization of the incident beam rotates by [16] …”