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Intermittent quakes and record dynamics in the thermoremanent magnetization of a spin-glass

A novel method for analyzing the intermittent behavior of linear response data in aging systems is presented and applied to spin-glass thermoremanent magnetization (TRM) (Rodriguez et al. Phys. Rev. Lett. 91, 037203, 2003). The probability density function (PDF) of magnetic fluctuations is shown to have an asymmetric exponential tail, demonstrating that the demagnetization process is carried by intermittent, significant, spin rearrangements or \emph{quakes}. These quakes are most pronounced shortly after the field removal, $t/t_w \approx 1$ and in the non-equilibrium aging regime $t/t_w >>1$. For a broad temperature range, we study the dependence of the TRM decay rate on $t$, the time since the initial quench and on $t_w$, the time at which the magnetic field is cut. The $t$ and $t_w$ dependence of the rate is extracted numerically from the data and described analytically using the assumption that the linear response is subordinated to the intermittent process which spasmodically release the initial imbalances created by the quench.