Dynamics of the Relaxation-Time Spectrum in a CuMn Spin-Glass

Lundgren, L.; Svedlindh, Peter; Nordblad, Per; Beckman, O.

doi:10.1103/physrevlett.51.911

Cited by 423 publications

(292 citation statements)

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“…Data analysis was performed by classical FFT methods, and within the frequency range of the first experiments, it was found that the power spectrum was stable and related by FDT to the out-of-phase susceptibility. 4,5 At the same period, the strong non-stationarity of spin glasses was experimentally detected 6,7 and related later to equivalent properties of glassy polymers already investigated long time before. 8 Very soon too, the non-stationarity of the very low frequency magnetic noise power spectrum was detected, 4 showing that the behavior of these systems is quite different when looking on different timescales.…”

Section: Introductionmentioning

confidence: 77%

Experimental investigation of the fluctuation dissipation relation in a spin glass

Hérisson

Ocio

2003

SPIE Proceedings

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We present the first experimental determination of the time auto-correlation of magnetization in the nonstationary regime of a spin glass, and its quantitative comparison with the corresponding response, the magnetic relaxation function. These measurements were performed in a new experimental setup working as an absolute thermometer. Clearly, we observe a non-linear fluctuation-dissipation relation between correlation and relaxation, i.e. an effective temperature higher than the bath temperature in the aging regime. According to theoretical developments on mean field models, and lately on short range ones, in the limit of very large waiting times, the relation between relaxation and correlation in the aging regime becomes temperature independent for a given system. A scaling procedure allows us to extrapolate to the limit of long waiting times by separating stationary and non-stationary regimes and to check the validity of the temperature independence of the fluctuation dissipation relation in the non-stationary regime.

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Section: Introductionmentioning

confidence: 77%

Experimental investigation of the fluctuation dissipation relation in a spin glass

Hérisson

Ocio

2003

SPIE Proceedings

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“…This is exactly a realization of the oscillator as a thermometer of Section II. From what we know from the time-scales of real spin-glasses [20,22], if the time after the quench is of the order of 10 minutes, and the period of the L-C circuit is of the order of the second, we are probing (at least partially) the aging regime: the temperature (defined as the average energy of the capacitor) should be different from the bath temperature. We believe that it would be interesting to return to the magnetization noise experiments [21] with the purpose of measuring the effective temperature: this would give us, for instance, useful insights into the nature of the spin-glass transition.…”

Section: Discussion Experimental Perspectives and Conclusionmentioning

confidence: 99%

“…This definition of the frequency-and waiting-time-dependent correlation C O (ω o , t w ) and out-ofphase susceptibility χ ′′ O (ω o , t w ) closely follows the actual experimental procedure for their measure: one considers a time window around t w consisting of a few cycles (so that phase and amplitude can be defined) and small enough respect to t w so that the measure is "as local as possible in time". In fact, these two quantities are standard in the experimental investigation of aging phenomena in spin-glasses [20][21][22].…”

Section: Frequency Dependent Thermometers That Measure Effectivementioning

confidence: 99%

Energy flow, partial equilibration, and effective temperatures in systems with slow dynamics

1997

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We show that, in nonequilibrium systems with small heat flows, there is a time-scale dependent effective temperature which plays the same role as the thermodynamical temperature, in that it controls the direction of heat flows and acts as a criterion for thermalization. We simultaneously treat the case of stationary systems with weak stirring and of glassy systems that age after cooling and show that they exhibit very similar behavior provided that time dependences are expressed in terms of the correlations of the system. We substantiate our claims with examples taken from solvable models with nontrivial low-temperature dynamics, but argue that they have a much wider range of validity. We suggest experimental checks of these ideas. 75.40.Gb, 75.10.Nr, Typeset using REVT E X 1

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“…dependence of the response of the system on the time in which it is perturbed. Aging effects [1] are a signature that the system is far from thermal equilibrium and consequently the fluctuation-dissipation theorem is not valid [2]. It has been realized quite recently that aging is indeed a solution of the off-equilibrium dynamics in some exactly solvable models [3,4].…”

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confidence: 99%

Aging in the linear harmonic oscillator

Bonilla

Padilla

Ritort

1998

Physica A: Statistical Mechanics and its Applications

126

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The low temperature Monte Carlo dynamics of an ensemble of linear harmonic oscillators shows some entropic barriers related to the difficulty of finding the directions in configurational space which decrease the energy. This mechanism is enough to observe some typical non-equilibrium features of glassy systems like activated-type behavior and aging in the correlation function and in the response function. Due to the absence of interactions the model only displays a one-step relaxation process.Slow relaxation processes are widespread in condensed matter physics. These include magnetic relaxation in spin glasses, transport processes in structural glasses, pinning effects in superconductors among others. A large class of these systems show what is commonly referred as aging, i.e. dependence of the response of the system on the time in which it is perturbed. Aging effects [1] are a signature that the system is far from thermal equilibrium and consequently the fluctuation-dissipation theorem is not valid [2]. It has been realized quite recently that aging is indeed a solution of the off-equilibrium dynamics in some exactly solvable models [3,4]. Aging appears if relaxation to the equilibrium is slow due to the presence of energy barriers in a rugged free energy landscape as well as in systems with entropy barriers with a quite simple landscape [5,6]. In this last case, as the system relaxes towards the equilibrium, the number of directions in phase space where the system can move decreases progressively. This means that the system needs more time to decorrelate or to forget the previous configuration. This effect is usually encoded in the two time correlation function where the C(t, t ′ ) depends on both time indices [7].From previous considerations it is clear that aging can also be present in extremely simple relaxing systems without any interaction, the only condition being the progressive reduction of available phase space where the energy decreases. This was an essential ingredient in the Backgammon model recently proposed to explain glassy behavior in the absence of energy barriers [5]. Here we consider a simpler example and analyze the Brownian oscillator. The Brownian oscillator is usually studied in the Langevin approach. It is described in any textbook of stochastic theory [8]. It is possible to show that in this case there are no slow processes involved. In fact, the relaxation turns out to be exponential as expected for the dynamics of a particle in a single parabolic potential well. Here we consider the Monte Carlo approach and choose a dynamics based on the Metropolis algorithm [9]. This Monte Carlo approach was already studied in a disordered model with long-range interactions which turns out to be non trivial, at least in the zero temperature limit [10]. The simplest case of an harmonic oscillator is solvable and we analyze the dynamics here.In [10] we checked that, after a suitable rescaling of time, the equilibrium Langevin and Monte Carlo dynamics are equivalent. Also, we showed how the Langevin dy...

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Dynamics of the Relaxation-Time Spectrum in a CuMn Spin-Glass

Cited by 423 publications

References 6 publications

Experimental investigation of the fluctuation dissipation relation in a spin glass

Experimental investigation of the fluctuation dissipation relation in a spin glass

Energy flow, partial equilibration, and effective temperatures in systems with slow dynamics

Aging in the linear harmonic oscillator

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