Relaxation and resonance in ferrofluids

Biomolecular reactions studied using changes in Brownian rotation dynamics of magnetic particles

“…Measurement of the complex frequency-dependent magnetic susceptibility is a standard characterisation method for magnetic liquids and magnetic particles with sizes below a few micrometer (Fannin et al, 1993;Hanson and Johansson, 1991). Using this method it is possible to determine and quantify the relaxation mechanisms of the magnetic particles.…”

Exceeding natural resonance frequency limit of monodisperse Fe3O4 nanoparticles via superparamagnetic relaxation

“…When the nanoparticle volume, V P , is reduced to a certain extent that magnetic anisotropy energy, KV P , is comparable to the thermal energy, k B T , there exists a finite probability that the magnetization vector will reverse its direction by thermal fluctuation at certain temperature T . Both theoretical and experimental data indicated that the frequency dependence of the susceptibility for a single domain particle depended on the ratio of the magnetic anisotropy energy to the thermal energy ( α = KV P / k B T )1516. In the case of , the real part of the complex susceptibility x ′( f ) decreases monotonically with increasing f , whilst the imaginary component, χ "( f ), has a maximum at a frequency f b = 1/ τ .…”

Imaging and Characterization of Magnetic Micro- and Nanostructures Using Force Microscopy

“…Characterization of Superparamagnetic Nanoparticles -Superparamagnetic materials are formed, if the size of a ferromagnetic domain is decreased to such small values that the sample magnetization is no longer stabilized (e.g., by crystal and shape anisotropy) against thermal fluctuations [156,157]. Hence, in the absence of a polarizing magnetic field, the sample's average magnetic moment vanishs.…”