1997/12/02 by Claudio Scherer, C. Scherer, Hans-Georg Matuttis +3
Biochemistry, Genetics and Molecular Biology · Engineering · Physics and Astronomy · #Characterization and Applications of Magnetic Nanoparticles #FOS: Physical sciences #Geomagnetism and Paleomagnetism Studies #Magnetic and Electromagnetic Effects #Statistical Mechanics (cond-mat.stat-mech) #cond-mat.stat-mech
paper · pdf · doi:10.48550/arxiv.cond-mat/9712025
21 pages, 6 figures, revtex
arxiv created 1997/12/02 · openalex publication_date 1997/12/02 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A new theory for the dynamics of the magnetic particles and their magnetic moments in ferrofluids is developed. Based on a generalized Lagrangian formulation for the equations of motion of the colloidal particle, we introduce its interaction with the solvent fluid via dissipative and random noise torques, as well as the interactions between the particle and its magnetic moment, treated as an independent physical entity and characterized by three generalized coordinates, its two polar angles and its modulus. It has been recognized recently that inertial effects, as well as the particle's rotational Brownian motion, may play important roles on the dynamic susceptibility of a class of magnetic fluids. No satisfactory theory existed, up to now, that takes this effects into account. The theory presented here is a first-principles 3-dimensional approach, in contrast to some phenomenological 2-dimensional approaches that can be found in the recent literature. It is appropriate for superparamagnetic, non-superparamagnetic and mixed magnetic fluids. As a simple application, the blocked limit (magnetic moment fixed in the particle) is treated numerically. The rotational trajectory of the particles in presence of a magnetic field, as well as the response functions and dynamic susceptibility matrices are explicitly calculated for some values of the parameters