Dynamics of magnetic nanoparticle in a viscous liquid: Application to magnetic nanoparticle hyperthermia

TLDR: In this paper, it was shown that the magnetic dynamics of an assembly of nanoparticles dispersed in a viscous liquid differs significantly from the behavior of the same assembly of particles immobilized in a solid matrix.

Abstract: It is shown that the magnetic dynamics of an assembly of nanoparticles dispersed in a viscous liquid differs significantly from the behavior of the same assembly of nanoparticles immobilized in a solid matrix. For an assembly of magnetic nanoparticles in a liquid two characteristic mode for stationary magnetization oscillations are found that can be called the viscous and magnetic modes, respectively. In the viscous mode, which occurs for small amplitude of the alternating magnetic field H0 as compared to the particle anisotropy field Hk, the particle rotates in the liquid as a whole. In a stationary motion the unit magnetization vector and the director, describing the spatial orientation of the particle, move in unison, but the phase of oscillations of these vectors is shifted relative to that of the alternating magnetic field. Therefore, for the viscous mode the energy absorption is mainly due to viscous losses associated with the particle rotation in the liquid. In the opposite regime, H0 ≥ Hk, the dir...