Dynamic magnetic response of a ferrofluid in a static uniform magnetic field

Abstract

Dynamic magnetic response of a ferrofluid in a static uniform magnetic fieldCitation for published version: Batrudinov, TM, Nekhoroshkova, YE, Paramonov, EI, Zverev, VS, Elfimova, EA, Ivanov, AO & Camp, PJ 2018, 'Dynamic magnetic response of a ferrofluid in a static uniform magnetic field', Physical Review E, vol. 98, no. 5. https://doi. AbstractA theory for the frequency-dependent magnetic susceptibility of a ferrofluid in a static uniform magnetic field is developed, including the dipolar interactions between the constituent particles.Interactions are included within the framework of modified mean-field theory. Predictions are given for the linear responses of the magnetization to a probing ac field both parallel and perpendicular to the static field, and are tested against results from Brownian dynamics simulations. The effects of particle concentration and dipolar coupling constant on the field-dependent static susceptibilities and the frequency dispersions are shown to be substantial, which justifies taking proper account of the interactions between particles. The theory is reliable provided that the volume concentration and dipolar coupling constant are not too large, and within the range of values for real ferrofluids.

Effects of interactions on magnetization relaxation dynamics in ferrofluids

“…(10)has been tested many times using experimental data and computer simulations both for static and dynamic magnetic properties. The main conclusion is that this simple approach gives a very good description of the effects of interactions, but the range of validity is limited to χ L < 3 for static properties such as the magnetization curve and initial susceptibility [10][11][12], and χ L < 1 for the dynamic initial magnetic susceptibility [40][41][42].…”

“…The dynamics of magnetic relaxation have been the subject of several experimental [28][29][30][31][32][33][34][35][36][37] and simulation [38][39][40][41][42][43][44][45][46] studies. Theoretically, the influence of the interactions on the so-called dynamic (or frequency-dependent) initial magnetic susceptibility has been evaluated within various approaches [41,42,[47][48][49][50][51][52][53][54]. Predictions from modified mean-field approaches (described below) have been tested critically against experimental [35,36] and simulation results [40][41][42].…”

“…Theoretically, the influence of the interactions on the so-called dynamic (or frequency-dependent) initial magnetic susceptibility has been evaluated within various approaches [41,42,[47][48][49][50][51][52][53][54]. Predictions from modified mean-field approaches (described below) have been tested critically against experimental [35,36] and simulation results [40][41][42].…”

“…The fluctuation-dissipation theorem links the decay of equilibrium thermal fluctuations in the magnetization with the linear response of the magnetization to small changes in the magnetic field. Specifically, the frequency spectrum of the magnetization autocorrelation function δM(t ) • δM(0) , where δM(t ) = M(t ) − M , is linked to the dynamic magnetic susceptibility, and this relation has been exploited in equilibrium dynamical simulations [40][41][42].…”

Generic theory of the dynamic magnetic response of ferrofluids

“…Field dependence of the peak frequencies (a-d) of imaginary-part dynamic susceptibility spectra and the static susceptibilities (e-f) normalized by their zero-field counterparts, for both the longitudinal ( ) and transverse (⊥) setups. Symbols are from BD simulations in Ref [31]. and lines are from my theoretical predictions.…”