Dynamical susceptibility of interacting superparamagnetic particles in a static magnetic field

Background and Objectives: Embedding a large number of magnetic nanoparticles into liquid or polymer matrix makes it possible to control the properties of a composite material using an external magnetic field. Such materials, so-calledmagnetic soft matter, include ferrofluids, magnetic elastomers, ferrogels, and various biocompatible magnetic filling. These complex systems attract a considerable amount of interest from researchers, medics and engineers because they are actively used in progressive high industrial and biomedical technologies. The dynamical response of an ensemble of interacting superparamagnetic particles in static and linearly polarized alternating magnetic fields is theoretically investigated. Materials and Methods: The rotational motion of the magnetic moment of a random ferroparticle is determined from the solution of the Fokker - Planck – Brown equation, which introduces an additional term that allows us to take into account the interparticle dipole-dipole interactions at the level of the modified first-order mean field theory. Results: The obtained analytical solutions for the probability density of the orientation of the magnetic moment of a random particle are used to determine the dynamical susceptibility. The spectrum of dynamical susceptibility is studied as a function of the static field strength, the magneto-crystallographic anisotropy parameter, the Langevin susceptibility of the ferroparticle ensemble, and the mutual orientation of the alternating and static magnetic fields. Conclusion: The obtained results represent essential information in the design and synthesis of new functional materials.