Abstract

PEREDO-ORTIZ, R.  and  HERNANDEZ-CONTRERAS, M.. Magnetic susceptibility of ferrofluids determined from diffusion coefficient of a tracer. Rev. mex. fis. [online]. 2022, vol.68, n.3, e031003.  Epub Apr 14, 2023. ISSN 0035-001X.  https://doi.org/10.31349/revmexfis.68.031003.

Linear response methods allow studying magnetic susceptibility relaxation in isotropic colloidal magnetic fluids. We show a relationship between the susceptibility of macroscopic magnetization at thermal equilibrium and the diffusion constant of a tracer particle. The comparison of the predicted frequency-dependent susceptibility with computer simulations shows their agreement. Besides, at a low concentration of particles, it has the expected Debye behavior. However, the initial susceptibility yields only the qualitative trends of the existing experiments at a low volume fraction of particles and its temperature dependence.

Keywords : Magnetic susceptibility; ferrofluid; nanoparticles; linear response.