Issue
EPL
Volume 84, Number 3, November 2008
Article Number 37011
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/84/37011
Published online 30 October 2008
EPL, 84 (2008) 37011
DOI: 10.1209/0295-5075/84/37011

Growth of a dynamical correlation length in an aging superspin glass

E. Wandersman1, V. Dupuis1, E. Dubois1, R. Perzynski1, S. Nakamae2 and E. Vincent2

1   Laboratoire des Liquides Ioniques et Interfaces Chargées, UMR 7612 CNRS, Université Pierre et Marie Curie, ESCPI - 4 place Jussieu, Boîte 51, 75252 Paris Cedex 05, France, EU
2   Service de Physique de l'Etat Condensé (CNRS URA 2464), DSM/IRAMIS/SPEC - CEA Saclay 91191 Gif-sur-Yvette Cedex, France, EU

wandersman@courriel.upmc.fr

received 2 June 2008; accepted in final form 1 October 2008; published November 2008
published online 30 October 2008

Abstract
We report on zero-field$\hbox{--} $cooled magnetization relaxation experiments on a concentrated frozen ferrofluid exhibiting a low-temperature superspin glass transition. With a method initially developed for spin glasses, we investigate the field dependence of the relaxations that take place after different aging times. We extract the typical number of correlated spins involved in the aging dynamics. This brings important insights into the dynamical correlation length and its time growth. Our results, consistent with expressions obtained for spin glasses, extend the generality of these behaviours to the class of superspin glasses. Since the typical flipping time is much larger for superspins than for atomic spins, our experiments probe a time regime much closer to that of numerical simulations.

PACS
75.50.Lk - Spin glasses and other random magnets.
75.50.Tt - Fine-particle systems; nanocrystalline materials.
75.40.Gb - Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.).

© EPLA 2008