Experimental Evidence of Fluctuation-Dissipation Theorem Violation in a Superspin Glass

Katsuyoshi Komatsu; D. L'Hote; Sawako Nakamae; Vincent Mosser; Marcin Konczykowski; Emmanuelle Dubois; V. Dupuis; Régine Perzynski

doi:10.1103/physrevlett.106.150603

arXiv · 1010.4012

Experimental Evidence of Fluctuation-Dissipation Theorem Violation in a Superspin Glass

Katsuyoshi Komatsu·D. L'Hote·Sawako Nakamae·Vincent Mosser·Marcin Konczykowski·Emmanuelle Dubois·V. Dupuis·Régine Perzynski

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Abstract

We present the experimental observation of the fluctuation-dissipation theorem (FDT) 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 $T_{\rm eff}$ 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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Katsuyoshi Komatsu, D. L'Hote, Sawako Nakamae, Vincent Mosser, Marcin Konczykowski, Emmanuelle Dubois, V. Dupuis, Régine Perzynski. 2011-01-07. Experimental Evidence of Fluctuation-Dissipation Theorem Violation in a Superspin Glass. https://doi.org/10.1103/physrevlett.106.150603

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