Ageing and memory phenomena in magnetic and transport properties of vortex matter

Nicodemi, Mario

doi:10.1088/0305-4470/34/41/303

Cited by 27 publications

(23 citation statements)

References 107 publications

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“…6 for r T RM and plotting the outcome versus log 10 t obs reproduces the well known shape of S(t): a broad maximum is present at t obs = t w , and a flat asymptotic value, equal to a, is reached for t obs ≫ t w . The asymptotically logarithmic TRM decay and, equivalently, the constant asymptotic value of S are widely observed in complex systems, To name a few cases, they are seen in switchable mirrors after UV illumination [27], in the field-cooled magnetization of spin glasses [28], and in the magnetic creep of the ROM model [29] of magnetic flux creep in type II superconductors [21]. In the asymptotic regime, the rate is r T RM ∝ 1/t, and the time at t w at which the perturbation is switched off is thus forgotten.…”

Section: Theorymentioning

confidence: 99%

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

Sibani¹,

Rodriguez

Kenning

2006

Phys. Rev. B

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A method for analyzing the intermittent behavior of linear response data in aging systems is presented and applied to the spin-glass thermoremanent magnetization (TRM) data of Rodriguez et al. (Phys. Rev. Lett. 91, 037203, 2003). The probability density function (PDF) of the magnetic fluctuations has an asymmetric exponential tail, showing that the demagnetization process occurs through intermittent spin rearrangements or quakes which significantly differ from reversible fluctuations having a Gaussian distribution with zero average. The intensity of quakes is determined by the TRM decay rate, which in turn depends on t, the time since the initial quench and on tw, the time at which the magnetic field is cut. For a broad range of temperatures, these dependences are extracted numerically from the data and described analytically using the assumption that the system's linear response is fully subordinated to the occurrence of the quakes which spasmodically release the imbalances created by the initial quench.

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Section: Theorymentioning

confidence: 99%

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

Sibani¹,

Rodriguez

Kenning

2006

Phys. Rev. B

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“…In addition to transient effects, pronounced memory effects and hysteretic V(I) curves have been observed near the peak effect in low temperature materials [2,[4][5][6][7][16][17][18][19][20]. Memory effects are also seen in simulations [22]. Xiao et al [7] have shown that transient behavior can lead to a strong dependence of the critical current on the current ramp rate.…”

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confidence: 98%

Metastability and transient effects in vortex matter near a decoupling transition

et al. 2003

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We examine metastable and transient effects both above and below the first-order decoupling line in a 3D simulation of magnetically interacting pancake vortices. We observe pronounced transient and history effects as well as supercooling and superheating between the 3D coupled, ordered and 2D decoupled, disordered phases. In the disordered supercooled state as a function of DC driving, reordering occurs through the formation of growing moving channels of the ordered phase. No channels form in the superheated region; instead the ordered state is homogeneously destroyed. When a sequence of current pulses is applied we observe memory effects. We find a ramp rate dependence of the V (I) curves on both sides of the decoupling transition. The critical current that we obtain depends on how the system is prepared.PACS numbers: 74.60Ge, 74.60JgVortices in superconductors represent an ideal system in which to study the effect of quenched disorder on elastic media. The competition between the flux-line interactions, which order the vortex lattice, and the defects in the sample, which disorder the vortex lattice, produce a remarkable variety of collective behavior [1]. One prominent example is the peak effect in low temperature superconductors, which appears near H c2 when a transition from an ordered to a strongly pinned disordered state occurs in the vortex lattice [2][3][4][5][6][7][8]. In high temperature superconductors, particularly BSCCO samples, a striking "second peak" phenomenon is observed in which a dramatic increase in the critical current occurs for increasing fields. It has been proposed that this is an order-disorder or 3D to 2D transition. [9][10][11][12][13] Recently there has been renewed interest in transient effects, which have been observed in voltage response versus time curves in low temperature superconductors [5][6][7][14][15][16][17]. In these experiments the voltage response increases or decays with time, depending on how the vortex lattice was prepared. The existence of transient states suggests that the disordered phase can be supercooled into the ordered region [21], producing an increasing voltage response, whereas the ordered phase may be superheated into the disordered region, giving a decaying response. In addition to transient effects, pronounced memory effects and hysteretic V(I) curves have been observed near the peak effect in low temperature materials [2,[4][5][6][7][16][17][18][19][20]. Memory effects are also seen in simulations [22]. Xiao et al. [7] have shown that transient behavior can lead to a strong dependence of the critical current on the current ramp rate. Recent neutron scattering experiments in conjunction with ac shaking have provided more direct evidence of supercooling and superheating near the peak effect [23]. Experiments on BSCCO have revealed that the high field disordered state can be supercooled to fields well below the second peak line [24]. Furthermore, transport experiments in BSCCO have shown metastability in the zero-field-cooled state near the second peak a...

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“…their properties slowly change with the waiting time, t w , elapsed from the quench. Ever since the initial observations in polymers [1], evidence has accumulated that spin-glasses [2], type II superconductors [3], glasses [4], and soft condensed matter [5], among others, age in similar ways, e.g. : For observation times t ≪ t w physical averages are nearly constant, and autocorrelations and their conjugate linear response functions are connected by an equilibrium-like fluctuation-dissipation theorem (FDT).…”

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confidence: 99%

Mesoscopic fluctuations and intermittency in aging dynamics

Sibani¹

2006

Europhys. Lett.

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PACS. 65.60.+a -Thermal properties of amorphous solids and glasses. PACS. 05.40.-a -Fluctuation phenomena, random processes, noise, and Brownian motion. PACS. 75.10.Nr -Spin-glass and other random models.Abstract. -Mesoscopic aging systems are characterized by large intermittent noise fluctuations. In a record dynamics scenario [P. Sibani and J. Dall, Europhys. Lett. 64, 2003] these events, quakes, are treated as a Poisson process with average α ln(1 + t/tw), where t is the observation time, tw is the age and α is a parameter. Assuming for simplicity that quakes constitute the only source of de-correlation, we present a model for the probability density function (PDF) of the configuration autocorrelation function. Beside α, the model has the average quake size 1/q as a parameter. The model autocorrelation PDF has a Gumbel-like shape, which approaches a Gaussian for large t/tw and becomes sharply peaked in the thermodynamic limit. Its average and variance, which are given analytically, depend on t/tw as a power-law and a power-law with a logarithmic correction, respectively. Most predictions are in good agreement with data from the literature and with the simulations of the Edwards-Anderson spin glass carried out as a test.Introduction. -After a rapid quench of an external parameter, e.g. the temperature, many complex materials age, i.e. their properties slowly change with the waiting time, t w , elapsed from the quench. Ever since the initial observations in polymers [1], evidence has accumulated that spin-glasses [2], type II superconductors [3], glasses [4], and soft condensed matter [5], among others, age in similar ways, e.g. : For observation times t ≪ t w physical averages are nearly constant, and autocorrelations and their conjugate linear response functions are connected by an equilibrium-like fluctuation-dissipation theorem (FDT). Conversely, for t ≫ t w they visibly drift and the FDT is violated. As was recently discovered, the drift happens in an intermittent fashion [6,7], i.e. through rare, large, and spatially heterogeneous re-arrangements, which appear as non-Gaussian tails in the probability density function (PDF) of configurational probes such as colloidal particle displacement [8,9] and correlation [10] or voltage noise fluctuations in glasses [11].As aging phenomena are similar for a broad class of interactions, we seek a mesoscopic description, and assume that intermittent events, for short quakes, are the main source of de-correlation in non-equilibrium aging. In the framework of record dynamics [12,13], quakes are irreversible and are triggered by (energy) fluctuations of record magnitude. We show how this leads to a description of the configurational autocorrelation function, more specifically, the dependence of the shape of its PDF on t, t w , the temperature T and the system size N , which resembles observations for colloidal gels [10] spin-glasses and kinetically constrained models [15,16]. The model PDF is closely approximated by the Gumbel distributions widely

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Ageing and memory phenomena in magnetic and transport properties of vortex matter

Cited by 27 publications

References 107 publications

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

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

Metastability and transient effects in vortex matter near a decoupling transition

Mesoscopic fluctuations and intermittency in aging dynamics

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