Order-Disorder Transitions in a Driven Magnetic Granular Monolayer
Lundi 12 octobre 2015 14:00
- Duree : 1 heure
Lieu : Conference room - LIPhy - Bât E - 140 Avenue de la Physique - St Martin d’Hères. Accès par interphone, appeler le secrétariat
Orateur : Simon MERMINOD (Lab. Matière et Systèmes Complexes (MSC), Univ. Paris 7, France)
Soft ferromagnetic particles are placed inside a horizontal, quasi-two-dimensional cell and are vertically vibrated, so that they perform a horizontal Brownian motion. When immersed in an external vertical magnetic field, the particles become magnetized and thus interact according to a dipolar repulsive law. Ordered and disordered phases are observed depending on the particle area fraction and on the ratio of the magnetic energy to the kinetic energy. At low particle area fraction, we show that, prior to the complete solidification of the disordered granular gas into a crystalline state, the typical properties of this dissipative granular gas progressively approach those expected for a usual gas at thermodynamic equilibrium.
Surprisingly, when the area fraction is higher, the system solidifies into a large-scale disordered labyrinthine phase mostly constituted of randomly orientated short chains of particles in contact. We characterize quantitatively this transition and explain the formation of these chains using a simple model. Moreover, we show that the labyrinthine phase exhibits slow dynamics.
Contact : eric.bertin@ujf-grenoble.fr
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