Magnetic susceptibility of ferrofluids determined from diffusion coefficient of a tracer

R Peredo-Ortiz and M Hernandez-Contreras, REVISTA MEXICANA DE FISICA, 68, 031003 (2022).

DOI: 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.

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