Glassy dynamics and aging in a dense ferrofluid

¹ European Synchrotron Radiation Facility - 6 rue Jules Horowitz BP 220, F-38043 Grenoble Cedex 9, France
² Laboratoire Liquides Ioniques et Interfaces Chargées, UMR 7612, Université Paris VI CNRS, ESPCI - 4 place Jussieu, 75252 Paris Cedex 05, France

Received: 15 February 2006
Accepted: 17 July 2006

Abstract

X-ray Photon Correlation Spectroscopy is used here to probe for the first time a glass-forming dispersion of repulsive particles spherical and sized. The highly concentrated colloidal system is based on the magnetic and charge-stabilized nanoparticles of a ferrofluid. Their out-of-equilibrium translational dynamics capture on nanoscale generic features usually observed on microscale: namely i) stretched exponential α relaxation with an exponent around 1.5 and ii) age-dependent characteristic time τ evolving from exponential at young ages to a slower behavior at large ages. τ is here scaling as in the whole experimental Q-range, below, on and above the scale of the interparticle distance, the driving force for aging in this glass-forming nanosystem being associated to larger scale rearrangements.