Fluctuation theory of magnetic relaxation for two-dimensional ensembles ofdipolar interacting nanoparticles - art. no. 184433

The fluctuation theory of magnetic relaxation has been developed for the tw o-dimensional ensembles of ferromagnetic nanoparticles. The particles have random locations on a square lattice, interact via dipolar interaction, and their easy axes of magnetization are perpendicular to the lattice plane. T he derivation of the equation that describes the time evolution of the magn etization has been based on the Fokker-Planck equation for the distribution function of a nanoparticle magnetic moment. The influence of the mean valu e and the fluctuations of the dipolar magnetic field on the process of magn etic relaxation is studied in detail. It has been shown that, in contrast t o the case of noninteracting nanoparticles which is characterized by the si ngle relaxation time, magnetic relaxation in those ensembles is characteriz ed by two different relaxation times. and that the rate of relaxation decre ases with Lime.