In our project, we investigate the conjecture that a dispersion of ferromagnetic particles in a magnetically neutral granular medium (ferrogranulate), once it is let to evolve from a fully homogeneous state under the influence of intrinsic magnetic forces, may also be regarded as a dynamically asymmetric mixture, in which the slow dynamics of magnetic particles coexists with the fast dynamics of a nonmagnetic component. Then the magnetized beads form a transient network that coarsens in time into compact clusters, resembling a viscoelastic phase separation (H. Tanaka 2000), where attached beads represent the slow phase. We investigate the phase separation of a shaken mixture of glass and magnetised steel spheres after a sudden quench of the shaker amplitude. After quenching, transient networks of steel spheres emerge in the experiment. In order to capture the origin for a viscoelastic phase separation as well as the long-time dynamics inaccessible in experiments, we use a simulation approach. The experimental results are compared with those of computer simulations. Coarse-grained molecular dynamics confirms the impact of an applied magnetic field on the structural transitions and allows to investigate long-time regimes and magnetic response not yet accessible in the experiment. It turns out that an applied magnetic field has different impacts, depending on it strength. It can be used either to slow down the dynamics of the structural transitions without changing the type of the resulting phases and only affecting the amount and sizes of clusters, or to fully impede the formatio network-like and compact aggregates of steel beads.

Simulation Snapshots

Examples of configuration snapshots when we applied external magnetic field perpendicular to the monolayer

Simulation snapshots corresponding to three different aria fraction of glass and magnetic particles, when the applied external magnetic field perpendicular to the monolayer