Diffusion-jump model for the combined Brownian and Neel relaxation dynamics of ferrofluids in the presence of external fields and flow
Ilg, P.
It is advisable to refer to the publisher's version if you intend to cite from this work. See Guidance on citing. To link to this item DOI: 10.1103/PhysRevE.100.022608 Abstract/SummaryRelaxation of suspended magnetic nanoparticles occurs via Brownian rotational diffusion of the particle as well as internal magnetization dynamics. The latter is often modeled by the stochastic Landau-Lifshitz equation, but its numerical treatment becomes prohibitively expensive in many practical applications due to a time-scale separation between fast, Larmor-type precession and slow, barrier-crossing dynamics. Here, a diffusion-jump model is proposed to take advantage of the time-scale separation and to approximate barrier-crossings as thermally activated jump processes that occur alongside rotational diffusion. The predictions of our diffusion-jump model are compared to reference results obtained by solving the stochastic Landau-Lifshitz equation coupled to rotational Brownian motion. Good agreement is found in the regime of high energy barriers where Neel relaxation can be considered a thermally activated rare event. While many works in the field have neglected N\'eel relaxation altogether, our approach opens the possibility to efficiently include Neel relaxation also into interacting many-particle models.
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