Effect of Mg-Al insertion on magnetotransport properties in epitaxial Fe/sputter-deposited MgAl2O4/Fe(001) magnetic tunnel junctions

Belmoubarik, Mohamed; Sukegawa, Hiroaki; Ohkubo, T.; Mitani, Seiji; Hono, K.

doi:10.1063/1.4973393

Cited by 6 publications

(2 citation statements)

References 24 publications

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“…Accordingly, the significant change in RA by the insertion can be correlated to the change in the temper ature dependence of G P and G AP through the difference in the electronic states at the bottom-MAO interface. The sign change of the slope in the temperature dependence of G P has been observed in several MTJs [9,24,25]. Two widely used models exist which describe the temperature dependence of conductance and TMR.…”

Section: Transport Propertiesmentioning

confidence: 96%

“…Similar to conventional MgO barriers, MAO barriers show the symmetry-filtering effect thorough the Δ 1 evanescent states [5,6]. Thus, large TMR ratios have been observed in the MTJs with various bcc-based ferromagnetic electrodes such as CoFe, Co 2 FeAl (CFA) Heusler alloy, and pure Fe [7][8][9]. Compared to MgO, the lattice spacing of MAO is well matched with those of the bcc ferromagnetic (FM) electrode materials.…”

Section: Introductionmentioning

confidence: 96%

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Comparative study of spin-dependent transport in Co₂FeAl/MgAl₂O₄/CoFe magnetic tunnel junctions with and without thin CoFe interface insertion: an elastic and inelastic scattering model analysis

Scheike¹,

Sukegawa²,

Ohkubo³

et al. 2019

J. Phys. D: Appl. Phys.

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We compare structural and transport properties of Co 2 FeAl (CFA)/MgAl 2 O 4 (MAO)/CoFe magnetic tunnel junctions (MTJs) with and without a 1 nm thick CoFe insertion layer. While the two MTJs show a large difference in resistance area (RA) product, there is no significant difference in their stacked structures such as the thickness of an MAO barrier. Temperature (T) dependence of tunneling conductance (G P and G AP for parallel and antiparallel configurations, respectively) was investigated for the two MTJs, as well as their tunnel magnetoresistance that exceeds 200%. The most striking feature of the temperature dependence is that nonmonotonic change appeared by inserting the CoFe layer, i.e. negative dG P /dT emerged only in the CFA/1 nm CoFe/MAO/CoFe MTJ. The observed results of G P and G AP were analyzed in a model proposed by Hu et al (2016 Phys. Rev. B 94, 094428), in which elastic (spin-conserved) and inelastic (spin-flip scattering) terms were considered. We found that the non-monotonic change observed in T dependence of G P is associated with dominance of the elastic tunneling term. This study demonstrated that the model analysis of T dependence of G P can give insight into the microscopic transport mechanism.

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Section: Transport Propertiesmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 96%

Comparative study of spin-dependent transport in Co₂FeAl/MgAl₂O₄/CoFe magnetic tunnel junctions with and without thin CoFe interface insertion: an elastic and inelastic scattering model analysis

Scheike¹,

Sukegawa²,

Ohkubo³

et al. 2019

J. Phys. D: Appl. Phys.

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Giant tunnel magnetoresistance in polycrystalline magnetic tunnel junctions with highly textured MgAl2O4(001) based barriers

Ikhtiar

Sukegawa

et al. 2018

Applied Physics Letters

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Although single-crystalline spinel (MgAl2O4)-based magnetic tunnel junctions (MTJs) are known to show a good bias voltage dependence of a tunnel magnetoresistance (TMR) ratio over MgO-based MTJs, no polycrystalline MgAl2O4-based MTJs exhibiting large TMR ratios have been grown previously due to the lack of crystallinity of the MgAl2O4 barrier. In this work, we demonstrate the growth of polycrystalline-based MTJs with large TMR ratios exceeding 240% and an improved bias voltage dependence compared to that of MgO-based MTJs. An ultra-thin CoFe/MgO seed layer on the amorphous CoFeB layer induced the growth of a highly (001)-textured MgAl2O4 barrier, which worked as a template layer for the solid epitaxy of CoFe grains during the crystallization of the CoFeB layers. High resolution scanning transmission electron microscopy shows lattice-matched epitaxy between the (001)-textured MgAl2O4 barrier and CoFe grains. This study demonstrates the industrial viability of MgAl2O4-based polycrystalline MTJs with an improved bias voltage dependence.

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Controlling oxygen distribution of an MgAl2O4 barrier for magnetic tunnel junctions by two-step process

Ichikawa

Cheng

Sukegawa

et al. 2020

Applied Physics Letters

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An MgAl2O4 barrier with an ordered spinel structure for magnetic tunnel junctions (MTJs) was prepared via a two-step process by repeating Mg–Al alloy deposition and post-oxidation to tune its oxidation state. The obtained Fe/MgAl2O4/Fe(001) epitaxial MTJs showed a large tunnel magnetoresistance (TMR) ratio (>150%) in a wide resistance × area (RA) range; this behavior was in contrast with that of MTJs prepared through a conventional one-step process, which exhibited a large TMR ratio only in a narrow RA range. The bias voltage at which the TMR is halved from the zero-bias value increased up to 1.20 and 1.47 V for the positive and negative bias polarities, respectively, when optimizing the two-step process. The nanostructure analysis revealed an improved oxygen distribution on the atomic scale in the MgAl2O4 barrier with the two-step process, providing a coherent barrier suitable for various practical applications.

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Effect of Mg-Al insertion on magnetotransport properties in epitaxial Fe/sputter-deposited MgAl2O4/Fe(001) magnetic tunnel junctions

Cited by 6 publications

References 24 publications

Comparative study of spin-dependent transport in Co₂FeAl/MgAl₂O₄/CoFe magnetic tunnel junctions with and without thin CoFe interface insertion: an elastic and inelastic scattering model analysis

Comparative study of spin-dependent transport in Co₂FeAl/MgAl₂O₄/CoFe magnetic tunnel junctions with and without thin CoFe interface insertion: an elastic and inelastic scattering model analysis

Giant tunnel magnetoresistance in polycrystalline magnetic tunnel junctions with highly textured MgAl2O4(001) based barriers

Controlling oxygen distribution of an MgAl2O4 barrier for magnetic tunnel junctions by two-step process

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Effect of Mg-Al insertion on magnetotransport properties in epitaxial Fe/sputter-deposited MgAl2O4/Fe(001) magnetic tunnel junctions

Cited by 6 publications

References 24 publications

Comparative study of spin-dependent transport in Co2FeAl/MgAl2O4/CoFe magnetic tunnel junctions with and without thin CoFe interface insertion: an elastic and inelastic scattering model analysis

Comparative study of spin-dependent transport in Co2FeAl/MgAl2O4/CoFe magnetic tunnel junctions with and without thin CoFe interface insertion: an elastic and inelastic scattering model analysis

Giant tunnel magnetoresistance in polycrystalline magnetic tunnel junctions with highly textured MgAl2O4(001) based barriers

Controlling oxygen distribution of an MgAl2O4 barrier for magnetic tunnel junctions by two-step process

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Comparative study of spin-dependent transport in Co₂FeAl/MgAl₂O₄/CoFe magnetic tunnel junctions with and without thin CoFe interface insertion: an elastic and inelastic scattering model analysis

Comparative study of spin-dependent transport in Co₂FeAl/MgAl₂O₄/CoFe magnetic tunnel junctions with and without thin CoFe interface insertion: an elastic and inelastic scattering model analysis