We present an extensive numerical study of the behaviour of a filament made of ferromagnetic colloidal particles subjected to the simultaneous action of a fluid flow and a stationary external magnetic field perpendicular to the flow lines. We found that in the presence of a shear flow, the tumbling motion observed at zero field is strongly inhibited when the external magnetic field is applied. The field is able to stabilise the filament with a well defined degree of alignment that depends on the balance between hydrodynamic and magnetic torques. In addition, for a Poiseuille flow, it has been found that the initial position has a long lasting influence on the behaviour of the magnetic filament when the external field is applied.
Abstract-In this work we present a characterization of the bidisperse ferrofluid microstructures that appear in thin layers of ferrofluid. These layers have been studied by a combination of Langevin dynamics simulations and density functional theory. Our results allow us to compare the microstructures that exist in quasi two dimensional ferrofluid nanolayers with the microstructures found in three dimensional bidisperse ferrofluids. Furthermore, our results allow us to explain the influence of the geometry of the sample on the topology and size distribution of the observed aggregates of magnetic nanoparticles.
The speed at which the magnetic perturbation or information propagates along a chain of classical dipoles is discussed. While in the quantum information counterpart for long‐range interacting spins, where the speed of propagation of the information plays a paramount role, it is not strictly clear whether a light cone exists or not, numerical evidence that interacting dipoles do posses a linear light cone shortly after a perturbation takes place in classical systems is provided. Specifically, a power‐law expansion occurs which is followed by a linear propagation of the associated perturbation. As opposed to the quantum case, and in analogy with the so‐called speed of gravity problem, it is found that the speed of propagation of information can be arbitrarily large in the classical context. While it is true that quantum information outperforms any classical treatment regarding many processes and properties, it is shown that for the case of spin buffers, classical chains of dipoles can indeed play a role as auxiliary tools in both quantum communications and processing.
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