Conduction electron scattering and spin-flipping at sputtered Al/Cu Interfaces

A. Sharma, N. Theodoropoulou, R. Loloee, W. P. Pratt, J. Bass, J. M. Zhang, M. A. Crimp, D. A. Cullen, David J. Smith, Kai Liu, Shuai Wang, Ke Xia

    Research output: Contribution to journalArticle

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    Abstract

    We use two different techniques to derive the two parameters describing conduction electron scattering and spin-flipping at sputtered Al/Cu interfaces in the current-perpendicular-to-plane (CPP) geometry. These parameters are: 2ARAl/Cu, twice the interface specific resistance, where A is the area through which the CPP current flows; and δAl/Cu, which gives the probability P of spin-flipping from P = 1 - exp(δ-). A technique involving simple multilayers, and sample temperature not exceeding room temperature, gives 2ARAl/Cu = 2.3 ± 0.2 fΩm2. A technique involving exchange-biased spin-valves (EBSVs), where the sample is annealed briefly to 453 K, gives 2ARAl/Cu = 2.0 ± 0.15 fΩm2. Averaging the two values, but increasing the uncertainty for reasons explained, gives the best estimate of 2ARAl/Cu 2.15 ± 0.4 fΩm2. This average is comparable to, but smaller than, the published value of 2ARAl/Cu 3.6 ± 1 fΩm 2 derived from thermal conductance measurements, and larger than our calculated values for interface thicknesses up to 6 monolayers (ML). However, it is similar to our calculated values for an interface thickness of 8 ML. Combining extrapolation of higher temperature bulk diffusion data for Al in Cu and vice-versa, with x-ray and transmission electron microscope (TEM) studies of similarly sputtered multilayers, indicates that such interface thicknesses are possible, especially for annealed multilayers. CPP-magnetoresistance (MR) measurements of the EBSV samples give only very small spin-flipping at the Al/Cu interface-δAl/Cu 0.05-0.05+0.02. Such a small value is consistent with expected small spin-orbit interactions in both Al and Cu. Supplementary studies of CPP-MR of Permalloy (Py)-based EBSVs containing [Cu/Al/Cu] trilayers, show unusual behavior when the central Al layer is at least 10 nm thick, giving a CPP-MR like that for Py/Al, independent of Cu layer thicknesses from 0 to 10 nm. MR, x-ray, and TEM results give some clues as to the origins of this behavior, but a completely satisfactory explanation is not yet available.

    Original languageEnglish (US)
    Article number053903
    JournalJournal of Applied Physics
    Volume109
    Issue number5
    DOIs
    StatePublished - Mar 1 2011

    Profile

    spin exchange
    Permalloys (trademark)
    electron spin
    conduction electrons
    electron scattering
    electron microscopes
    spin-orbit interactions
    extrapolation
    room temperature
    estimates
    geometry
    temperature

    ASJC Scopus subject areas

    • Physics and Astronomy(all)

    Cite this

    Sharma, A., Theodoropoulou, N., Loloee, R., Pratt, W. P., Bass, J., Zhang, J. M., ... Xia, K. (2011). Conduction electron scattering and spin-flipping at sputtered Al/Cu Interfaces. Journal of Applied Physics, 109(5), [053903]. DOI: 10.1063/1.3549688

    Conduction electron scattering and spin-flipping at sputtered Al/Cu Interfaces. / Sharma, A.; Theodoropoulou, N.; Loloee, R.; Pratt, W. P.; Bass, J.; Zhang, J. M.; Crimp, M. A.; Cullen, D. A.; Smith, David J.; Liu, Kai; Wang, Shuai; Xia, Ke.

    In: Journal of Applied Physics, Vol. 109, No. 5, 053903, 01.03.2011.

    Research output: Contribution to journalArticle

    Sharma, A, Theodoropoulou, N, Loloee, R, Pratt, WP, Bass, J, Zhang, JM, Crimp, MA, Cullen, DA, Smith, DJ, Liu, K, Wang, S & Xia, K 2011, 'Conduction electron scattering and spin-flipping at sputtered Al/Cu Interfaces' Journal of Applied Physics, vol 109, no. 5, 053903. DOI: 10.1063/1.3549688
    Sharma A, Theodoropoulou N, Loloee R, Pratt WP, Bass J, Zhang JM et al. Conduction electron scattering and spin-flipping at sputtered Al/Cu Interfaces. Journal of Applied Physics. 2011 Mar 1;109(5). 053903. Available from, DOI: 10.1063/1.3549688

    Sharma, A.; Theodoropoulou, N.; Loloee, R.; Pratt, W. P.; Bass, J.; Zhang, J. M.; Crimp, M. A.; Cullen, D. A.; Smith, David J.; Liu, Kai; Wang, Shuai; Xia, Ke / Conduction electron scattering and spin-flipping at sputtered Al/Cu Interfaces.

    In: Journal of Applied Physics, Vol. 109, No. 5, 053903, 01.03.2011.

    Research output: Contribution to journalArticle

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    abstract = "We use two different techniques to derive the two parameters describing conduction electron scattering and spin-flipping at sputtered Al/Cu interfaces in the current-perpendicular-to-plane (CPP) geometry. These parameters are: 2ARAl/Cu, twice the interface specific resistance, where A is the area through which the CPP current flows; and δAl/Cu, which gives the probability P of spin-flipping from P = 1 - exp(δ-). A technique involving simple multilayers, and sample temperature not exceeding room temperature, gives 2ARAl/Cu = 2.3 ± 0.2 fΩm2. A technique involving exchange-biased spin-valves (EBSVs), where the sample is annealed briefly to 453 K, gives 2ARAl/Cu = 2.0 ± 0.15 fΩm2. Averaging the two values, but increasing the uncertainty for reasons explained, gives the best estimate of 2ARAl/Cu 2.15 ± 0.4 fΩm2. This average is comparable to, but smaller than, the published value of 2ARAl/Cu 3.6 ± 1 fΩm 2 derived from thermal conductance measurements, and larger than our calculated values for interface thicknesses up to 6 monolayers (ML). However, it is similar to our calculated values for an interface thickness of 8 ML. Combining extrapolation of higher temperature bulk diffusion data for Al in Cu and vice-versa, with x-ray and transmission electron microscope (TEM) studies of similarly sputtered multilayers, indicates that such interface thicknesses are possible, especially for annealed multilayers. CPP-magnetoresistance (MR) measurements of the EBSV samples give only very small spin-flipping at the Al/Cu interface-δAl/Cu 0.05-0.05+0.02. Such a small value is consistent with expected small spin-orbit interactions in both Al and Cu. Supplementary studies of CPP-MR of Permalloy (Py)-based EBSVs containing [Cu/Al/Cu] trilayers, show unusual behavior when the central Al layer is at least 10 nm thick, giving a CPP-MR like that for Py/Al, independent of Cu layer thicknesses from 0 to 10 nm. MR, x-ray, and TEM results give some clues as to the origins of this behavior, but a completely satisfactory explanation is not yet available.",
    author = "A. Sharma and N. Theodoropoulou and R. Loloee and Pratt, {W. P.} and J. Bass and Zhang, {J. M.} and Crimp, {M. A.} and Cullen, {D. A.} and Smith, {David J.} and Kai Liu and Shuai Wang and Ke Xia",
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    AU - Bass,J.

    AU - Zhang,J. M.

    AU - Crimp,M. A.

    AU - Cullen,D. A.

    AU - Smith,David J.

    AU - Liu,Kai

    AU - Wang,Shuai

    AU - Xia,Ke

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    N2 - We use two different techniques to derive the two parameters describing conduction electron scattering and spin-flipping at sputtered Al/Cu interfaces in the current-perpendicular-to-plane (CPP) geometry. These parameters are: 2ARAl/Cu, twice the interface specific resistance, where A is the area through which the CPP current flows; and δAl/Cu, which gives the probability P of spin-flipping from P = 1 - exp(δ-). A technique involving simple multilayers, and sample temperature not exceeding room temperature, gives 2ARAl/Cu = 2.3 ± 0.2 fΩm2. A technique involving exchange-biased spin-valves (EBSVs), where the sample is annealed briefly to 453 K, gives 2ARAl/Cu = 2.0 ± 0.15 fΩm2. Averaging the two values, but increasing the uncertainty for reasons explained, gives the best estimate of 2ARAl/Cu 2.15 ± 0.4 fΩm2. This average is comparable to, but smaller than, the published value of 2ARAl/Cu 3.6 ± 1 fΩm 2 derived from thermal conductance measurements, and larger than our calculated values for interface thicknesses up to 6 monolayers (ML). However, it is similar to our calculated values for an interface thickness of 8 ML. Combining extrapolation of higher temperature bulk diffusion data for Al in Cu and vice-versa, with x-ray and transmission electron microscope (TEM) studies of similarly sputtered multilayers, indicates that such interface thicknesses are possible, especially for annealed multilayers. CPP-magnetoresistance (MR) measurements of the EBSV samples give only very small spin-flipping at the Al/Cu interface-δAl/Cu 0.05-0.05+0.02. Such a small value is consistent with expected small spin-orbit interactions in both Al and Cu. Supplementary studies of CPP-MR of Permalloy (Py)-based EBSVs containing [Cu/Al/Cu] trilayers, show unusual behavior when the central Al layer is at least 10 nm thick, giving a CPP-MR like that for Py/Al, independent of Cu layer thicknesses from 0 to 10 nm. MR, x-ray, and TEM results give some clues as to the origins of this behavior, but a completely satisfactory explanation is not yet available.

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