Extraction of a dynamical correlation length in a superspin glass

Elie Wandersman (1) , V. Dupuis (1) , Emmanuelle Dubois (1) , Régine Perzynski (1) , Sawako Nakamae (2) , Eric Vincent (2)

1 LI2C - Liquides Ioniques et Interfaces Chargées
2 SPEC - UMR3680 - Service de physique de l'état condensé

In this paper we report on zero field cooled magnetization relaxation experiments on a concentrated frozen ferrofluid exhibiting a low temperature superspin glass transition. Using a method initially developped for spin glasses we are able to extract the dynamical correlation length and its time dependence from the Zeeman coupling between the applied magnetic field and the typical number of correlated spins participating in the dynamics. Our results are in general agreement with the expressions obtained for spin glasses and extend the generality of these behaviors to the class of superspin glasses. Additionnaly, since the typical flipping time for thermally activated dynamics over the anisotropy barrier is much larger for superspins than for atomic spins our experiments are probing a time regime which is much closer to that probed in numerical simulations.

Mots clés: magnetic nanoparticles; spin glasses; slow dynamics; aging; correlation length

Domaines: Systèmes désordonnés et réseaux de neurones [cond-mat.dis-nn]

Elie Wandersman, V. Dupuis, Emmanuelle Dubois, Régine Perzynski, Sawako Nakamae, et al.. Extraction of a dynamical correlation length in a superspin glass. EPL - Europhysics Letters, 2008, 84, pp.37011. ⟨10.1209/0295-5075/84/37011⟩. ⟨hal-00284743v1⟩