Europhys. Lett.
Volume 75, Number 5, September 2006
Page(s) 764 - 770
Section Condensed matter: structural, mechanical and thermal properties
Published online 02 August 2006
Europhys. Lett., 75 (5), pp. 764-770 (2006)
DOI: 10.1209/epl/i2006-10179-4

Glassy dynamics and aging in a dense ferrofluid

A. Robert1, E. Wandersman2, E. Dubois2, V. Dupuis2 and R. Perzynski2

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 in final form 17 July 2006
published online 2 August 2006

X-ray Photon Correlation Spectroscopy is used here to probe for the first time a glass-forming dispersion of repulsive particles spherical and $10\un{nm}$ 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 $\alpha$ relaxation with an exponent around 1.5 and ii) age-dependent characteristic time $\tau$ evolving from exponential at young ages to a slower behavior at large ages. $\tau$ is here scaling as Q-1 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.

61.10.-i - X-ray diffraction and scattering.
82.70.Dd - Colloids.
64.70.Pf - Glass transitions.

© EDP Sciences 2006