Control of perpendicular magnetic anisotropy at the Fe/MgO interface by phthalocyanine insertion

Sakamoto, Shoya; Jackson, Edward A.; Kawabe, Takahiro; Tsukahara, Takuya; Kotani, Yoshinori; Toyoki, Kentaro; Minamitani, Emi; Miura, Yoshio; Nakamura, Tetsuya; Hirohata, Atsufumi; Miwa, Shinji

doi:10.1103/physrevb.105.184414

Cited by 8 publications

(4 citation statements)

References 33 publications

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“…Figure 2(b) shows the XAS spectra with the background subtracted. The XAS spectrum of the LiF-free Fe/MgO multilayer looks identical to those reported in previous studies [40][41][42][43]; the XAS spectrum has a broad single peak for each of the Fe L 2,3 edges and does not exhibit multiplet features. This is also the case for the spectra with LiF insertion, except that there is a slight variation in XAS spectral line shape because of the spectral overlap between F K and Fe L 2,3 edges.…”

Section: Resultssupporting

confidence: 83%

The origin of enhanced interfacial perpendicular magnetic anisotropy in LiF-inserted Fe/MgO interface

Sakamoto¹,

Nozaki²,

Yuasa³

et al. 2022

Preprint

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The Fe/MgO interface is an essential ingredient in spintronics as it shows giant tunneling magnetoresistance and strong perpendicular magnetic anisotropy (PMA). A recent study demonstrated that the insertion of an ultra-thin LiF layer between the Fe and MgO layers enhances PMA significantly. In this study, we perform x-ray magnetic circular dichroism measurements on Fe/LiF/MgO multilayers to reveal the origin of the PMA enhancement. We find that the LiF insertion increases the orbital-magnetic-moment anisotropy and thus the magnetic anisotropy energy. We attribute the origin of this orbital-magnetic-moment-anisotropy enhancement to the stronger electron localization and electron-electron correlation or the better interface quality with fewer defects.

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Section: Resultssupporting

confidence: 83%

The origin of enhanced interfacial perpendicular magnetic anisotropy in LiF-inserted Fe/MgO interface

Sakamoto¹,

Nozaki²,

Yuasa³

et al. 2022

Preprint

Self Cite

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“…[ 44 , 45 ] Bruno's tight‐binding model, which has been validated by experiments for a magnetic interface with the SOC strength ( ζ SO ) << the bandwidth of the FM, [ 45 , 46 , 47 , 48 ] predicts K s ∝ ζ SO ∆ m orb , where ∆ m orb is the orbital moment anisotropy of the interface. Given that ∆ m orb of the GaAs/CoFe interface (∆ m orb ≈ 0.085 µ B ) is only slightly greater than that of MgO/CoFe interface (∆ m orb ≈ 0.056 µ B , see Section S2 in the Supporting Information) as suggested by X‐ray magnetic circular dichroism experiments, [ 49 , 50 , 51 , 52 , 53 ] the 20 times greater K s of the GaAs/CoFe interface than the MgO/CoFe interface reveals considerably stronger interfacial SOC than the MgO/CoFe interface. Therefore, the observation that the sin2 φ signal is much stronger for the MgO/CoFe than for the GaAs/CoFe strongly disagrees with the previous speculation that the sin2 φ second HHV signal arose from an interfacial SOC effect.…”

Section: Sample Details and Measurement Techniquesmentioning

confidence: 99%

Absence of Spin‐Orbit Torque and Discovery of Anisotropic Planar Nernst Effect in CoFe Single Crystal

2023

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Exploration of exotic spin polarizations in single crystals is of increasing interest. A current of longitudinal spins, the so‐called “Dresselhaus‐like” spin current, which is forbidden in materials lacking certain inversion asymmetries, is implied to be generated by a charge current at the interface of single‐crystal CoFe. This work reports unambiguous evidence that there is no indication of spin current of any spin polarizations from the interface or bulk of single‐crystalline CoFe and that the sin2φ second harmonic Hall voltage, which is previously assumed to signify Dresselhaus‐like spin current, is not related to any spin currents but rather a planar Nernst voltage induced by a longitudinal temperature gradient within the sample. Such sin2φ signal is independent of large applied magnetic fields and interfacial spin‐orbit coupling, inversely correlated to the heat capacity of the substrates and overlayers, quadratic in charge current, and appears also in polycrystalline ferromagnets. Strikingly, the planar Nernst effect (PNE) in the CoFe single crystal has a strong fourfold anisotropy and varies with the crystalline orientation. Such strong, anisotropic PNE has widespread impacts on the analyses of a variety of spintronic experiments and opens a new avenue for the development of PNE‐based thermoelectric battery and sensor applications.

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“…with large tunneling magnetoresistance ratio, high thermal stability, and relatively low switching current density for applications of high-density MRAM [1]. Therefore, the origin of the PMA in the nonmagnetic/CoFeB/MgO systems has been extensively studied in the last decade and is still under debate so far [2][3][4][5][6][7][8]. Theoretical calculations suggest that the hybridization between the 3d orbitals of Fe/Co and 2p orbitals of O and the oxidation condition at the CoFeB/MgO interface plays a critical role in PMA of ultrathin nonmagnetic/CoFe-B/MgO junctions [5].…”

Section: Introductionmentioning

confidence: 99%

Perpendicular magnetic anisotropy of Cr/CoFeB/MgO modulated by MgO thickness

Guo,

Huang,

et al. 2024

J. Phys. D: Appl. Phys.

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The dependence of perpendicular magnetic anisotropy (PMA) on the MgO thickness in Cr/CoFeB/MgO/Ta films has been experimentally investigated. A clear PMA is observed in the as-deposited samples with 1.8 nm MgO while no as-deposited PMA is shown in those with 4.0 nm MgO. This may be attributed to the moderate oxidation degree of CoFeB and larger interfacial anisotropy energy density K i to overcome the volume magnetic anisotropy and demagnetization field. On the contrary, samples with 4.0 nm MgO demonstrate PMA only after annealing, which might be due to the oxygen and boron diffusion during the annealing process. These results would provide a method to optimize the design of CoFeB/MgO structures on 3d metals for future applications in perpendicular magnetic devices.

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Control of perpendicular magnetic anisotropy at the Fe/MgO interface by phthalocyanine insertion

Cited by 8 publications

References 33 publications

The origin of enhanced interfacial perpendicular magnetic anisotropy in LiF-inserted Fe/MgO interface

The origin of enhanced interfacial perpendicular magnetic anisotropy in LiF-inserted Fe/MgO interface

Absence of Spin‐Orbit Torque and Discovery of Anisotropic Planar Nernst Effect in CoFe Single Crystal

Perpendicular magnetic anisotropy of Cr/CoFeB/MgO modulated by MgO thickness

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