Velocity statistics of dynamic spinners in out-of-equilibrium magnetic suspensions

Alexey Snezhko, Igor Aronson

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

We report on the velocity statistics of an out-of-equilibrium magnetic suspension in a spinner phase confined at a liquid interface. The suspension is energized by a uniaxial alternating magnetic field applied parallel to the interface. In a certain range of the magnetic field parameters the system spontaneously undergoes a transition into a dynamic spinner phase (ensemble of hydrodynamically coupled magnetic micro-rotors) comprised of two subsystems: self-assembled spinning chains and a gas of rotating single particles. Both subsystems coexist in a dynamic equilibrium via continuous exchange of the particles. Spinners excite surface flows that significantly increase particle velocity correlations in the system. For both subsystems the velocity distributions are strongly non-Maxwellian with nearly exponential high-energy tails, P(v) ∼ exp(-v/v0). The kurtosis, the measure of the deviation from the Gaussian statistics, is influenced by the frequency of the external magnetic field. We show that in the single-particle gas the dissipation is mostly collisional, whereas the viscous damping dominates over collisional dissipation for the self-assembled spinners. The dissipation increases with the frequency of the applied magnetic field. Our results provide insights into non-trivial dissipation mechanisms determining self-assembly processes in out-of-equilibrium magnetic suspensions.

Original languageEnglish (US)
Pages (from-to)6055-6061
Number of pages7
JournalSoft Matter
Volume11
Issue number30
DOIs
StatePublished - Aug 14 2015

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Condensed Matter Physics

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