Off-equilibrium fluctuation-dissipation relation in a spin glass

TL;DR

This paper presents experimental verification of the fluctuation-dissipation relation in an insulating spin glass, exploring both equilibrium and aging dynamics, and introduces a scaling method to approach the separation of time-scales.

Contribution

It provides the first experimental measurement of the off-equilibrium fluctuation-dissipation relation in a spin glass, including a method to analyze aging dynamics.

Findings

Fluctuation-dissipation theorem holds in quasi-equilibrium regime.

Deviations occur in the aging regime.

A scaling procedure approaches the separation of time-scales.

Abstract

We report new experimental results obtained onthe insulating spin glass CdCrInS_4. Our experimental setup allows a quantitative comparison between thethermo-remanent magnetization and the autocorrelation of spontaneous fluctuations of magnetization, yielding acomplete determination of the fluctuation-dissipationrelation. The dynamics can be studied both in thequasi-equilibrium regime, where the fluctuation-dissipation theorem holds, and in the deeply aging regime. The limit of separation of time-scales, as used in analytical calculations, can be approached by use of a scaling procedure.