Course 10: Fluctuation Dissipation Relation in a Non-stationary System: Experimental Investigation in a Spin Glass
Abstract
We present the first experimental determination of the time autocorrelation of magnetization C( ) in the aging regime of a spin glass, and its quantitative comparison with the corresponding response, the relaxation of magnetization ( ). These measurements were performed in a new experimental setup equivalent to an absolute thermometer. Clearly, we observe a non-linear fluctuation dissipation relation between and C: at large C (short observation times ) fluctuation dissipation theorem is obeyed, while in the aging regime (small correlation and large ), the fluctuation dissipation relation is driven by an effective temperature higher than the bath temperature. According to theoretical predictions on mean field models, and lately on short range ones, in the limit of large waiting times , the (C) relation in the aging regime is temperature independent for a given system. A scaling procedure allows us to extrapolate to the limit of long waiting times by separating stationary and nonstationary contributions in both and C, and to check the validity of these predictions.
- Publication:
-
Slow Relaxations and Nonequilibrium Dynamics in Condensed Matter
- Pub Date:
- 2004
- Bibcode:
- 2004srnd.conf..605O