Magnetic relaxation of a system of superparamagnetic particles weakly coupled by dipole-dipole interactions
Abstract
Long range dipole-dipole interactions in the thermal fluctuations of the magnetization of an assembly of single-domain ferromagnetic particles are considered, ignoring orientational correlations between the particles, so that the evolution of the magnetization orientations may be described by a nonlinear Fokker-Planck equation (FPE) reducing to the usual linear one in the limit of infinite dilution [W. F. Brown Jr., Phys. Rev. 130, 1677 (1963)]. The thermally activated relaxation time scale of the assembly is estimated, leading to a simple and transparent modification of the axially symmetric asymptotes for the superparamagnetic relaxation time.
- Publication:
-
Journal of Applied Physics
- Pub Date:
- December 2011
- DOI:
- 10.1063/1.3665886
- arXiv:
- arXiv:1109.4294
- Bibcode:
- 2011JAP...110k3921D
- Keywords:
-
- ferromagnetic materials;
- ferromagnetic relaxation;
- Fokker-Planck equation;
- magnetic moments;
- magnetic particles;
- magnetisation;
- superparamagnetism;
- 75.30.Cr;
- 75.40.Mg;
- 75.50.Tt;
- 75.60.Ej;
- 76.50.+g;
- 75.20.-g;
- Saturation moments and magnetic susceptibilities;
- Numerical simulation studies;
- Fine-particle systems;
- nanocrystalline materials;
- Magnetization curves hysteresis Barkhausen and related effects;
- Ferromagnetic antiferromagnetic and ferrimagnetic resonances;
- spin-wave resonance;
- Diamagnetism paramagnetism and superparamagnetism;
- Condensed Matter - Statistical Mechanics
- E-Print:
- 31 pages, 3 figures, regular article