Conductance fluctuations of mesoscopic spin glasses

Vegvar, P. G. N. de; Lévy, Laurent; Fulton, T. A.

doi:10.1103/physrevlett.66.2380

Cited by 73 publications

(52 citation statements)

References 21 publications

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“…The latter value is close to¸P for the undoped Cu sample suggesting the complete suppression of spin-scattering in high magnetic "eld. A similar B dependence of¸P was observed previously in Cu : Mn rings with c"1000 ppm [3].…”

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confidence: 71%

“…at a much lower value for B3 [0, 3 T]. These results demonstrate the recovery of phase coherence due to spin-glass correlations and a strong magnetic "eld.2000 Elsevier Science B.V. All rights reserved.Keywords: Mesoscopics; Phase coherent transport; Spin-glasses; Spin scattering Universal conductance #uctuations (UCF) arising from quantum interferences between di!erent electron paths [1] can be used to probe the complex frozen magnetic order in metallic spin-glasses [2,3]. Here we report on UCF in Cu : Mn nanocontacts with a Mn concentration c between 31 and 920 ppm, encompassing the transition from the single-impurity regime to the spin-glass state.…”

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Universal conductance fluctuations in Cu : Mn nanocontacts

Löhneysen

Paschke

Weber

et al. 2000

Physica B: Condensed Matter

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Universal conductance #uctuations in Cu : Mn nano-contacts of di!erent Mn concentrations c yield the phase coherence length¸P which exhibits a minimum at c+100 ppm. Above this concentration which marks the onset of a spin-glass state below 0.2 K,¸P depends on the magnetic "eld range, rising to nearly the c"0 value for B3 [9.5, 12.5 T] and leveling-o! at a much lower value for B3 [0, 3 T]. These results demonstrate the recovery of phase coherence due to spin-glass correlations and a strong magnetic "eld.2000 Elsevier Science B.V. All rights reserved.Keywords: Mesoscopics; Phase coherent transport; Spin-glasses; Spin scattering Universal conductance #uctuations (UCF) arising from quantum interferences between di!erent electron paths [1] can be used to probe the complex frozen magnetic order in metallic spin-glasses [2,3]. Here we report on UCF in Cu : Mn nanocontacts with a Mn concentration c between 31 and 920 ppm, encompassing the transition from the single-impurity regime to the spin-glass state. We estimate the spin-glass temperature for our thin samples ¹ "0.06, 0.43 and 1.08 K for 31, 315 and 920 ppm Mn, respectively [4].The samples were fabricated by electron-beam lithography followed by #ash-evaporation and lift-o! in a two-lead geometry. The contact width w varies between 60 and 480 nm, and the length¸between 100 and 2000 nm. The Cu : Mn "lms (thickness 10}20 nm) were mounted within the mixing chamber of a He}He dilution refrigerator with a base temperature of ¹+0.05 K.A typical R(B) curve is shown in Fig. 1a. The sample with c"920 ppm exhibits a resistance (R) maximum at B"0. The negative magnetoresistance (MR) arises from the suppression of spin}#ip scattering by the magnetic "eld B. The resistance #uctuations R obtained from the R(B) data by subtracting the negative MR using a spline "t, yield the conductance #uctuations G"! R/R , where R is the resistance of the nanobridge, i.e. the contribution of the contact leads subtracted from R (R "17.7 for the sample of Fig. 1). Fig. 1b shows G whose amplitude increases with the magnetic "eld. G(B) #uctuates on a magnetic-"eld scale B which is determined by the magnetic #ux "B A A P through a phase-coherent region A P where "h/e. A P is bounded by the width w of the sample and the phase coherence length¸P if w(¸P (¸[1]. Therefore, P may be estimated from the correlation "eld B "/w¸P which corresponds to the HWHM of the autocorrelation function of G(B) [1]. This simple relation has been veri"ed for Au and Ag nanowires of widths between 45 and 340 nm [5]. Combining the results of B for samples with the same c but di!erent w, a linear "t B versus w\ gives an estimate for¸P.We calculated a low-"eld (B)3 T) and a high-"eld (B*9.5 T) B for the di!erent samples, yielding¸P (cf. Fig. 2). The large error in¸P is caused by the small number of samples (2}4) for each c as well as an uncertainty in the data analysis due to the restricted "eld range. Furthermore, the simple relation B &¸\ P may be violated by up to 20% in the case of spin}orbit scattering [6].Two reg...

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supporting

confidence: 71%

mentioning

confidence: 99%

Universal conductance fluctuations in Cu : Mn nanocontacts

Löhneysen

Paschke

Weber

et al. 2000

Physica B: Condensed Matter

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“…Similar experiments by Meyer and Weissman on AuFe samples reveal deviations from both the droplet model and the hierarchical model for mesoscopic sample sizes. 15 Measurements by de Vegvar et al 16 on mesoscopic CuMn wires with a Mn concentration of 0.1 at. % indicate the presence of a magnetofingerprint that is stable in time.…”

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confidence: 99%

Universal conductance fluctuations and low-temperature1/fnoise in mesoscopic AuFe spin glasses

et al. 2000

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We report on intrinsic time-dependent conductance fluctuations observed in mesoscopic AuFe spin-glass wires. These dynamical fluctuations have a 1/f -like spectrum and appear below the measured spin-glass freezing temperature of our samples. The dependence of the fluctuation amplitude on temperature, magnetic field, voltage, and Fe concentration allows a consistent interpretation in terms of quantum interference effects, that are sensitive to the slowly fluctuating spin configuration.

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“…In a spin-glass phase, the perturbing potential associated with the frozen spins leads to the violation of the Onsager-Bűttiker symmetry relations in mesoscopic samples [13][14][15] as well as it alters the scaling factor of the UCF amplitude [5,7]. The fluctuating spins, in turn, because of an extreme sensitivity of the conductance to potential realizations, are expected to be an efficient source of the conductance noise [7-8,l,16].…”

Section: Spin-disorder Scatteringmentioning

confidence: 99%

Influence of Magnetic Impurities upon Universal conductance Fluctuations

Dietl

1997

Acta Phys. Pol. A

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Mesoscopic phenomena in quantum structures which incorporate magnetic impurities with localized spins may exhibit a number of novel features driven by spin-disorder scattering, exchange spin-splitting of electron bands, and the formation of bound magnetic polarons. After brief information on these effects, their influence on universal conductance fluctuations as well as on low frequency noise and quantum localization is presented. Millikelvin investigations of diffusive charge transport, which have been carried out for submicron wires of n+-Cdi_ x Mnx Te epilayers, are reviewed in some details. These studies have provided information on the significance of spin-disorder scattering in semiconductors and put into the evidence a new driving mechanism of the magnetoconductance fluctuations -the redistribution of the electrons between energy levels of the system, induced by the giant s-d exchange spin-splitting. Important implications of these findings for previous interpretations of spin effects in semiconductor and metal nanostructures are discussed.

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Conductance fluctuations of mesoscopic spin glasses

Cited by 73 publications

References 21 publications

Universal conductance fluctuations in Cu : Mn nanocontacts

Universal conductance fluctuations in Cu : Mn nanocontacts

Universal conductance fluctuations and low-temperature1/fnoise in mesoscopic AuFe spin glasses

Influence of Magnetic Impurities upon Universal conductance Fluctuations

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