Theoretical-field description of the critical behavior in ferromagnetic nanoparticles structured ensemble

S V Belim

Abstract

The paper explores the critical behaviour of a ferromagnetic nanoparticle structured ensemble within a theoretical-field approach in three-dimensional space. Critical behaviour has been investigated in the transition from the superparamagnetic to the ferromagnetic phases. Individual nanoparticles are considered in the investigated system instead of point spins. Interaction between spins is carried out only by means of dipole-dipole forces. In this case, the interaction is anisotropic. The calculations are made in a two-loop approximation. The method Pade-Borel for summing asymptotic series is used. Critical exponents are calculated (ν = 0.635, η = 0.347, γ = 1.050, β = 0.427, α = 0.095, δ = 3.456). This system had a new class of critical behaviour. A comparison was made with the results of actual experiments.