Correlation between symmetry-selective transport and spin-dependent resonant tunneling in fully epitaxial Cr/ultrathin-Fe/MgO/Fe(001) magnetic tunnel junctions

Niizeki, Tomohiko; Sukegawa, Hiroaki; Mitani, Seiji; Tezuka, Nobuki; Inomata, K.

doi:10.1063/1.3647578

Cited by 4 publications

(2 citation statements)

References 18 publications

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“…The Mg layer was inserted to protect oxidation during the MgO deposition. 22 The MgO barrier was deposited at RT using EBevaporation of a sintered MgO plate (Kojundo Chemical Laboratory Co., LTD.) with a back pressure Pdepo of ~1  10 5 Pa and deposition rate of 810 3 nm/s. For the wedge-shaped MgO barrier, we used a linear motion shutter between the MgO plate and the substrate.…”

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confidence: 99%

Exceeding 400% tunnel magnetoresistance at room temperature in epitaxial Fe/MgO/Fe(001) spin-valve-type magnetic tunnel junctions

Scheike

Xiang

Wen

et al. 2021

Applied Physics Letters

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Giant tunnel magnetoresistance (TMR) ratios of 417% at room temperature (RT) and 914% at 3 K were demonstrated in epitaxial Fe/MgO/Fe(001) exchanged-biased spin-valve magnetic tunnel junctions (MTJs) by tuning growth conditions for each layer, combining sputter deposition for the Fe layers, electron-beam evaporation of the MgO barrier, and barrier interface tuning. Clear TMR oscillation as a function of the MgO thickness with a large peak-to-valley difference of ~80% was observed when the layers were grown on a highly (001)-oriented Cr buffer layer. Specific features of the observed MTJs are symmetric differential conductance (dI/dV) spectra for the bias polarity and plateau-like deep local minima in dI/dV (parallel configuration) at |V| = 0.2~0.5 V. At 3K, fine structures with two dips emerge in the plateau-like dI/dV, reflecting highly coherent tunneling through the Fe/MgO/Fe. We also observed a 496% TMR ratio at RT by a 2.24-nm-thick-CoFe insertion at the bottom-Fe/MgO interface.

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confidence: 99%

Exceeding 400% tunnel magnetoresistance at room temperature in epitaxial Fe/MgO/Fe(001) spin-valve-type magnetic tunnel junctions

Scheike

Xiang

Wen

et al. 2021

Applied Physics Letters

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“…Therefore, TMR ratio can be drastically enhanced or reduced only by a minor modification of these interfaces states; such as the insertion of an ultrathin metallic layer. [18][19][20] In our previous report, ultrathin Mg-Al (Mg10Al90 atomic%) was inserted between the bottom-Fe electrode and direct-sputtered MgAl2O4 barrier of Fe/MgAl2O4/Fe MTJs in order to tune the interface condition. 16 However, a systematic study on the Mg-Al insertion effect has yet to be investigated.…”

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

et al. 2016

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We investigated the effect of an Mg-Al layer insertion at the bottom interface of epitaxial Fe/MgAl2O4/Fe(001) magnetic tunnel junctions (MTJs) on their spin-dependent transport properties. The tunnel magnetoresistance (TMR) ratio and differential conductance spectra for the parallel magnetic configuration exhibited clear dependence on the inserted Mg-Al thickness.A slight Mg-Al insertion (thickness < 0.1 nm) was effective for obtaining a large TMR ratio above 200% at room temperature and observing a distinct local minimum structure in conductance spectra. In contrast, thicker Mg-Al (> 0.2 nm) induced a reduction of TMR ratios and featureless conductance spectra, indicating a degradation of the bottom-Fe/MgAl2O4 interface.Therefore, a minimal Mg-Al insertion was found to be effective to maximize the TMR ratio for a sputtered MgAl2O4-based MTJ.

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Interface resonance in Fe/Pt/MgO multilayer structure with large voltage controlled magnetic anisotropy change

Jibiki

Goto

Tsujikawa

et al. 2019

Applied Physics Letters

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Electric control of magnetism has been a topic of interest for various spintronic applications. It is known that monoatomic Pt layer insertion at the Fe/MgO interface increases voltage-controlled magnetic anisotropy (VCMA). However, the reason for the optimality of this thickness has not been explained thus far. In this study, we observed the changes in the electronic states at the Fe/MgO interface using tunneling spectroscopy on an epitaxial Fe(001)/Pt/MgO(001) structure to characterize the density of states around the Fermi level. We found that a surface resonant state is formed at the Fermi level by the insertion of a monoatomic Pt layer, which is consistent with our first principles study. In addition, the VCMA enhancement owing to the formation of this surface resonance state agrees with the recently proposed microscopic theory.

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Correlation between symmetry-selective transport and spin-dependent resonant tunneling in fully epitaxial Cr/ultrathin-Fe/MgO/Fe(001) magnetic tunnel junctions

Cited by 4 publications

References 18 publications

Exceeding 400% tunnel magnetoresistance at room temperature in epitaxial Fe/MgO/Fe(001) spin-valve-type magnetic tunnel junctions

Exceeding 400% tunnel magnetoresistance at room temperature in epitaxial Fe/MgO/Fe(001) spin-valve-type magnetic tunnel junctions

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

Interface resonance in Fe/Pt/MgO multilayer structure with large voltage controlled magnetic anisotropy change

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