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Updated: Dec 27, 2025

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Experimental evidence for violation of the fluctuation-dissipation theorem in a superspin glass
Katsuyoshi Komatsu1, Denis L'Hôte, Sawako Nakamae
1Service de Physique de l'Etat Condensé (CNRS/URA 2464), DSM/IRAMIS/SPEC, CEA Saclay, F-91191 Gif/Yvette Cedex, France. katsuyoshi.komatsu@cea.fr
Abstract:
We present the experimental observation of the fluctuation-dissipation theorem violation in an assembly of interacting magnetic nanoparticles in the low temperature superspin-glass phase. The magnetic noise is measured with a two-dimension electron gas Hall probe and compared to the out of phase ac susceptibility of the same ferrofluid. For "intermediate" aging times of the order of 1 h, the ratio of the effective temperature T(eff) to the bath temperature T grows from 1 to 6.5 when T is lowered from T(g) to 0.3 T(g), regardless of the noise frequency. These values are comparable to those measured in an atomic spin glass as well as those calculated for a Heisenberg spin glass.
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