Approach to equilibrium of a spin-glass (original) (raw)
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Time decay of the saturated remanent magnetization in a metallic spin glass
Physical review. B, Condensed matter, 1987
The time decay of the saturated remanent magnetization (M,) has been studied in the amorphous metallic spin glass (Fep|SNip85)75P|6B6A13. This relaxation, which by nature is different from the zero-field equilibrium relaxation, shows at low temperatures (T/Ts & 0.98) a time variation accurately described by a pure power law. At temperatures in the immediate vicinity of Tg, the experimental time decay can be described by a power law times a stretched exponential functional form: M, Mpt exp[-(t/rr)' "l. Spin glasses are known to exhibit slow, nonexponential relaxation. This kind of dynamical behavior is a characteristic feature of disordered, strongly interacting systems of condensed matter. The response function of dielectrics, ' glasses, and glassy polymers resembles that of spin glasses. In particular, it has been experimentally shown that spin glasses display aging phenomena, a behavior that is well known from other glassy materials. This implies that the spin-glass "phase" is a thermodynamic nonequilibrium state. In spin glasses aging is revealed by a dependence of the response function on the wait-time t
A reversion of magnetization decay in spin glasses
New Journal of Physics, 2010
Reversion of thermoremanent magnetization decay is observed in a canonical spin glass; that is, the system is remagnetized despite the absence of a magnetic field. This unexpected phenomenon occurs only when the system is heated or cooled back to the temperature T 0 at which it was previously subjected to a magnetic field for a significant length of time. Therefore, this reversion can be interpreted as a restoration of the spin state existing before at T 0 . This new information will be a key to resolving a long-standing controversy regarding the nature of spin glasses.
Deviations from Full Aging in Numerical Spin Glass Models
2003
The deviations from full or pure aging behavior, i.e. perfect t/twt/t_wt/tw scaling of the correlation and response functions of aging glassy systems, are not well understood theoretically. Recent experiments of Rodriguez et al. (Phys. Rev. Lett. 91, 037203 (2003)) have shown that full aging applies to the thermoremanent magnetization in the limit of infinite cooling rate during the initial quench.
Spin-glass dynamics in the presence of a magnetic field: exploration of microscopic properties
Journal of Statistical Mechanics: Theory and Experiment, 2021
The synergy between experiment, theory, and simulations enables a microscopic analysis of spin-glass dynamics in a magnetic field in the vicinity of and below the spin-glass transition temperature T g. The spin-glass correlation length, ξ(t, t w; T), is analysed both in experiments and in simulations in terms of the waiting time t w after the spin glass has been cooled down to a stabilised measuring temperature T < T g and of the time t after the magnetic field is changed. This correlation length is extracted experimentally for a CuMn 6 at. % single crystal, as well as for simulations on the Janus II special-purpose supercomputer, the latter with time and length scales comparable to experiment. The non-linear magnetic susceptibility is reported from experiment and simulations, using ξ(t, t w; T) as the scaling variable. Previous experiments are reanalysed, and disagreements about the nature of the Zeeman energy are resolved. The growth of the spin-glass magnetisation in zero-fiel...
Time dependent critical field transition line in an insulating spin-glass
Journal de Physique Lettres, 1983
2014 Nous avons analysé le retour à l'équilibre de l'aimantation dans Eu0,4Sr0,6S pour différents temps de mesure (1 ms-1 s) après coupure d'un petit champ magnétique superposé à un grand champ statique. Nous déduisons, pour les diverses échelles de temps, différentes lignes de transition champ-température, qui chacune suit la loi de De Almeida-Thouless. L'échelle de champ dépend (ne dépend pas) du temps pour des temps de mesure supérieurs (inférieurs) à 10 ms. Nous proposons une interprétation des résultats au vu de récentes théories. Abstract 2014 The change in magnetization of the insulating spin-glass Eu0.4Sr0.6S has been measured as a function of time (1 ms-1 s) for small magnetic field changes superposed on a larger constant field. A set of field-temperature transition lines has been obtained for different time scales. Each appears to be of the De Almeida-Thouless form but with a field scale which is dependent (independent) of the time scale for times > () 10 ms. The results are analysed in terms of recent theories.
Intermittent quakes and record dynamics in the thermoremanent magnetization of a spin-glass
Physical Review B, 2006
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.
Mean-field theory of temperature cycling experiments in spin glasses
Physical Review B, 1999
We study analytically the effect of temperature cyclings in mean-field spinglasses. In accordance with real experiments, we obtain a strong reinitialization of the dynamics on decreasing the temperature combined with memory effects when the original high temperature is restored. The same calculation applied to meanfield models of structural glasses shows no such reinitialization, again in accordance with experiments. In this context, we derive some relations between experimentally accessible quantities and propose new experimental protocols. Finally, we briefly discuss the effect of field cyclings during isothermal aging.
Nuclear Physics B - Proceedings Supplements, 1988
Experimental results on the relaxation of the magnetization of spin glasses at temperatures below the spin glass freezing temperature Tg show very similar behaviour for different spin glass materials. Some data on relaxation are presented and discussed in the context of a droplet scaling theory for the spin glass phase elaborated by Fisher and Huse (Phys Rev. B, in print).
Nonequilibrium Spin-Glass Dynamics from Picoseconds to a Tenth of a Second
Physical Review Letters, 2008
We study numerically the nonequilibrium dynamics of the Ising Spin Glass, for a time that spans eleven orders of magnitude, thus approaching the experimentally relevant scale (i.e. seconds). We introduce novel analysis techniques that allow to compute the coherence length in a modelindependent way. Besides, we present strong evidence for a replicon correlator and for overlap equivalence. The emerging picture is compatible with non-coarsening behavior. PACS numbers: 75.50.Lk, 75.40.Gb, 75.40.Mg Spin Glasses[1] (SG) exhibit remarkable features, including slow dynamics and a complex space of states: their understanding is a key problem in condensedmatter physics that enjoys a paradigmatic status because of its many applications to glassy behavior, optimization, biology, financial markets, social dynamics.
Physical Review Letters, 2001
A new protocol of the zero-field-cooled (ZFC) magnetization process is studied experimentally on an Ising spin-glass (SG) Fe$_{0.50}$Mn$_{0.50}$TiO$_3$ and numerically on the Edwards-Anderson Ising SG model. Although the time scales differ very much between the experiment and the simulation, the behavior of the ZFC magnetization observed in the two systems can be interpreted by means of a common scaling expression based on the droplet picture. The results strongly suggest that the SG coherence length, or the mean size of droplet excitations, involved even in the experimental ZFC process, is about a hundred lattice distances or less.