Figure 3.

Brownian, Néel and effective relaxation time in dependence of the particle volume. A spherical magnetite particle with a magnetic core (purple area) encapsulated by a hydrodynamic shell (grey area) of thickness t is assumed: (a) Brownian relaxation time in dependence of the magnetic particle core diameter for hydrodynamic shell thicknesses of 10 nm (solid line) and 20 nm (dashed line). While an increase of the hydrodynamic shell thickness affects the Brownian relaxation time of small particles at short relaxation times, particle clustering induces large changes of the relaxation time less dependent of the initial particle size; (b) Brownian, Néel and effective relaxation time as functions of the magnetic core diameter [112].