The extra-dimension W = kT Ln (t/τ0) of phase space below the spin glass transition : an experimental study of the relaxation of the magnetization at constant field in CuMn

Abstract

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Equilibrium and off-equilibrium simulations of the Gaussian spin glass

“…In fig.7 we plot the results either for t w = 0 and for t w = 0. We note that both fits are compatible with the linear dependence in the temperature predicted from the experimental measurements [17]. In the region t w /t ≥ 32 we have performed the analysis assuming that the correlation function could be factorized as…”

“…The relevance of the variable T log(t) has been observed in experiments on magnetic remanence in a wide region [17]. We call off-equilibrium correlation length, ξ(t), the typical distance over which the system is thermalized after a time t. For this domain growth the SRSB picture predicts a power law [9] ξ(t) ∝ t 1/z(T ) ,…”

On the stochastic transport in disordered systems

“…The observed tw dependence of the finite-frequency response X (w ) is in fact the kind of ageing phenomena, which are well-known in spin-glass and polymer-glass physics [4,5,6]. It should be noted that the power-law behaviour 3m x ( w ) ~ w K itself could be easily interpreted in terms of the multitude of modes with an exponential distribution of energy barriers ; however, the fact that this behaviour is accompanied by ageing is less trivial and indicates the highly correlated nature of dynamics involved.…”

“…The interest in the subject is based upon the fact that 1D RWRF appeared to mimic surprisingly well the time evolution phenomena of a wide variety of disordered systems. The dispersive transport in amorphous semiconductors [1][2], spin-slip dynamics on fractals [3] or relaxation of magnetization in spin-glasses [4,5] can be mentioned as the most striking examples. In this paper we consider the particle propagating over 1D random force medium under the action of extra driven force and find the ac response of this system.…”

Comment on ‘‘Flux trapping and superconductive glass state inLa2CuO4−

“…In Cu:Mn(5 at.%), a failure in this Tlnit/ro) scaling signals the collapse of the P(W) distribution at the spinglass transition T c s =29 K which is much higher than D where the remanent vanishes at the time scale of static measurements. 2,3 In the superconductor, likewise, point D is most certainly a function of T In (//TO) and belongs to a time-dependent curve of the (H,T) plane which cannot be a transition line. In the absence of further evidence it is misleading to speak of a "superconductive glass" state and to hint, in this way, that there is in the hysteresis of these systems (with these fields) much more than was observed in type-II superconductors with pinning.…”