Absence of weak electron localization in (Co/Pt)n-multilayer-nanowires with perpendicular anisotropy

Brands, M.; Carl, A.; Dumpich, G.

doi:10.1002/andp.200510163

Cited by 4 publications

(12 citation statements)

References 25 publications

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“…The decreasing conductance with decreasing temperature can be well described by EEI, as already shown for other ferromagnetic metals. [8][9][10][11] The excellent agreement of the parameters F 2D and F 1D found in the ferromagnets investigated up to now underlines the universal character of EEI. The size of the WL correction is expected to be of the same order as EEI at zero field.…”

Section: Discussionsupporting

confidence: 70%

“…29 In our permalloy square one obtains a parameter F 2D = 2.0, using a slope of 0.65 as shown in Fig. 3͑a͒ 9 In Fe and Ni the parameters are comparable to the parameter observed in Co. 10 We note that the effect of EEI is rather small in the quasi-two-dimensional film. The relative conductivity change ⌬ / from 1 K to 35 mK is only ϳ8 ϫ 10 −4 .…”

Section: Electron-electron Interaction In 1d and 2d Samplessupporting

confidence: 66%

“…Up to now several experimental works explore this question showing that WL is absent in Co, 8,10 Fe, 10 Ni, 11 and Co/Pt multilayers. 9 In the ferromagnetic semiconductor ͑Ga,Mn͒As, having a rather small internal magnetic induction, weak localization was observed. 13,14 As theory claims that WL does not get suppressed by internal magnetic induction, 30,31 the question arises why WL can be observed in ͑Ga,Mn͒As but not in Co, Fe, Ni, or Co/Pt multilayers.…”

Section: Electron-electron Interaction In 1d and 2d Samplesmentioning

confidence: 99%

“…Up to now no clear signature of weak localization was found in any ferromagnetic metal. For example, the conductances of Co, 5,8 Co/Pt multilayers, 9 Fe, 10 and Ni ͑Ref. 11͒ were not affected by weak localization.…”

Section: Introductionmentioning

confidence: 98%

“…In these materials a decreasing conductance with decreasing temperature was ascribed to electronelectron interaction. 5,[8][9][10][11] However, in the ferromagnetic semiconductor ͑Ga,Mn͒As ͑Ref. 12͒ weak localization corrections could be observed quite recently.…”

Section: Introductionmentioning

confidence: 99%

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Quantum transport in ferromagnetic permalloy nanostructures

2008

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We studied phase-coherent phenomena in mesoscopic permalloy ͑Ni 81 Fe 19 ͒ samples by exploring lowtemperature transport. Both differential conductance as a function of bias voltage and magnetoconductance of individual wires display conductance fluctuations. Analysis of these fluctuations yields a phase coherence length of ϳ250 nm at 25 mK as well as a 1 / ͱ T temperature dependence. To suppress conductance fluctuations by ensemble averaging, we investigated low-temperature transport in wire arrays and extended permalloy films. In these samples we have measured conductance corrections which stem from electron-electron interaction; but attempts to detect signatures of weak localization were without success.

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Section: Discussionsupporting

confidence: 70%

Section: Electron-electron Interaction In 1d and 2d Samplessupporting

confidence: 66%

Section: Electron-electron Interaction In 1d and 2d Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Quantum transport in ferromagnetic permalloy nanostructures

2008

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Influence of growth parameters on the perpendicular magnetic anisotropy of [Co/Ni] multilayers and its temperature dependence

Posth

Hassel

Spasova

et al. 2009

Journal of Applied Physics

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[Co/Ni] multilayer films are grown in various conditions to study the influence of growth parameters on the anisotropy of the films in order to optimize the perpendicular uniaxial anisotropy. These multilayers are expected to be useful for current induced magnetization switching experiments due to its softmagnetic behavior by which the critical current density can be reduced dramatically. The polycrystalline films are prepared by electron beam evaporation with varying buffer layer, cap layer, as well as Co layer thickness and number of repetitions of Co and Ni layers. Measurements of the magneto-optic Kerr effect, ferromagnetic resonance, and superconducting quantum interference device magnetometry are used to analyze the magnetic anisotropy and magnetization. Depending on the magnitude of the uniaxial anisotropy, the overall easy direction of magnetization is orientated either in plane or out of plane depending on the amplitude of the demagnetization field. Moreover, we present the results for the temperature dependence of the uniaxial anisotropy and the magnetization of the [Co/Ni] film from 5 up to 420 K, which is close to the Curie temperature.

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All-Electrical Measurement of the Density of States in (Ga,Mn)As

et al. 2009

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We report on electrical measurements of the effective density of states in the ferromagnetic semiconductor material (Ga,Mn)As. By analyzing the conductivity correction due to enhanced electronelectron interaction the electrical diffusion constant was extracted for (Ga,Mn)As samples of different dimensionality. Using the Einstein relation allows to deduce the effective density of states of (Ga,Mn)As at the Fermi energy.PACS numbers: 75.50.Pp, The ferromagnetic semiconductor (Ga,Mn)As [1] has been studied intensely over the last decade and has become a model system for future spintronics applications [2,3]. With typical Mn-concentrations between 1 % and 15 % maximum Curie temperatures of up to ∼ 180 K have been reported [4,5]. Mn atoms on Ga-sites provide both holes and magnetic moments. For Mn concentrations larger than 1 % the impurity wavefunctions at the Fermi energy overlap and a metallic state forms. The ferromagnetic order between the magnetic moments of the Mn-ions is mediated by the delocalized holes [6]. A topic of current debate is whether the holes reside in an impurity band, detached and above the valence band or in the valence band [7]. A mean field picture based on the latter scenario allowed to predict, e.g. Curie temperature [6] or magnetocrystalline anisotropies [8] in (Ga,Mn)As correctly. On the other hand optical absorption experiments, carried out, e.g. in Ref. [9,10], suggest that even for high manganese concentrations of up to 7 % the Fermi energy stays in an impurity band, detached from the valence band, with a high effective hole mass of order ten free electron masses m e [9]. However, there is also indication that the impurity band and the valence band have completely merged as discussed in Ref. [7] and references therein. In the present letter we make use of the well known quantum mechanical conductivity correction due to electron-electron interaction (EEI) to extract the diffusion constant and hence the density of states at the Fermi energy, N (E F ). The electrically measured values of N (E F ) will be compared with recent theoretical calculations.In ferromagnetic (Ga,Mn)As the conductivity is decreasing with decreasing temperature below 10 K. This conductivity decrease can be explained by enhanced electron-electron interaction [11]. The effect of EEI arises from a modified screening of the Coulomb-potential due to the carriers' diffusive motion and depends on the dimensionality of the conductor [12]. As the conductivity decrease due to enhanced electron-electron interaction is depending on the electrical diffusion constant D, a detailed analysis of the conductivity decrease, different for different dimensionality, provides experimental access to the diffusion constant. Using the Einstein relation σ = N (E F )De 2 , with the conductivity σ, the effective density of states at Fermi's energy, N (E F ), can be determined.To investigate electron-electron interaction in quasi 1D, 2D and 3D systems we fabricated Hall-bar mesas (2D and 3D) and wire arrays (1D and crossover regime from 1D to ...

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Absence of weak electron localization in (Co/Pt)n-multilayer-nanowires with perpendicular anisotropy

Cited by 4 publications

References 25 publications

Quantum transport in ferromagnetic permalloy nanostructures

Quantum transport in ferromagnetic permalloy nanostructures

Influence of growth parameters on the perpendicular magnetic anisotropy of [Co/Ni] multilayers and its temperature dependence

All-Electrical Measurement of the Density of States in (Ga,Mn)As

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