Ferroelectrically tunable magnetic skyrmions in ultrathin oxide heterostructures

Wang, Lingfei; Feng, Qiyuan; Kim, Yoonkoo; Kim, Rokyeon; Lee, Ki Hoon; Pollard, Shawn; Shin, Yoo Jin; Zhou, Haibiao; Peng, Wei; Lee, Daesu; Meng, Wenjie; Yang, Hyunsoo; Han, Jung Hoon; Kim, Miyoung; Lu, Qingyou; Noh, Tae Won

doi:10.1038/s41563-018-0204-4

Cited by 309 publications

(272 citation statements)

References 52 publications

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“…We note that all published transport results comprising similar phenomenology [17][18][19][20][21][22][23][24] could be well explained using our model introducing two coexisting ferromagnetic orders. Moreover our explanation successfully describes every electrical transport feature, including dependence on magnetic field, gate voltage, temperature and thin film parameters such as doping level and film thickness, without the need to speculate about new topological physics.…”

supporting

confidence: 76%

“…The anomalous Hall effect (AHE), despite being first reported over a hundred years ago, [1] remains of significant modern research interest as its investigation in novel magnetic materials continues to yield rich physics. Recent examples of this are the quantum anomalous Hall effect [2][3][4][5][6][7][8][9][10][11][12], which offers both potential for metrological applications [13,14] and for the academic study of axion electrodynamics [5,12,15,16], as well as reports on alleged contribution to the Hall effect [17][18][19][20][21][22][23][24] associated with skyrmion magnetic textures.…”

mentioning

confidence: 99%

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Coexistence of Surface and Bulk Ferromagnetism Mimics Skyrmion Hall Effect in a Topological Insulator

Fijalkowski¹,

Hartl²,

Winnerlein³

et al. 2020

Phys. Rev. X

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Here we report the investigation of the anomalous Hall effect in the magnetically doped topological insulator (V,Bi,Sb)2Te3. We find it contains two contributions of opposite sign. Both components are found to depend differently on carrier density, leading to a sign inversion of the total anomalous Hall effect as a function of applied gate voltage. The two contributions are found to have different magnetization reversal fields, which in combination with a temperature dependent study points towards the coexistence of two ferromagnetic orders in the system. Moreover, we find that the sign of total anomalous Hall response of the system depends on the thickness and magnetic doping density of the magnetic layer. The thickness dependence suggests that the two ferromagnetic components originate from the surface and bulk of the magnetic topological insulator film. We believe that our observations provide insight on the magnetic behavior, and thus will contribute to an eventual understanding of the origin of magnetism in this material class. In addition, our data bears a striking resemblance to anomalous Hall signals often associated with skyrmion contributions. Our analysis provides a straightforward explanation for both the magnetic field dependence of the Hall signal and the observed change in sign without needing to invoke skyrmions, and thus suggest that caution is needed when making claims of effects from skyrmion phases. arXiv:1912.02766v1 [cond-mat.mes-hall]

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supporting

confidence: 76%

mentioning

confidence: 99%

Coexistence of Surface and Bulk Ferromagnetism Mimics Skyrmion Hall Effect in a Topological Insulator

Fijalkowski¹,

Hartl²,

Winnerlein³

et al. 2020

Phys. Rev. X

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“…Hall resistivity measurements on SrRuO 3 films coupled to adjacent SrIrO 3 layers indeed showed signatures of a topological Hall effect [10,11]. Further work on SrRuO 3 films interfaced to ferroelectric films with off-centering B-site distortions [12] and ferromagnetic films with strong mutual antiferromagnetic coupling [13] yielded similar signatures. However, since these kind of structures show complex strain states [14] and intricate oxygen octahedra rotation patterns [15], it is an open question whether the Hall effect signatures are truly a proof for the presence of skyrmions.…”

Section: Introductionmentioning

confidence: 71%

Unconventional anomalous Hall effect driven by oxygen-octahedra-tailoring of the SrRuO₃ structure

2019

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The anomalous Hall effect of SrRuO 3 is of special interest, since Weyl nodes appear in the band structure and lead to an unconventional temperature dependence of the anomalous Hall constant. Moreover, it has been proposed that coupling of SrRuO 3 films to materials with strong spin-orbit coupling or with ferroelectric or ferromagnetic order might lead to the formation of skyrmions and a topological contribution to the Hall effect. This latter conjecture is strongly debated. We probed this proposal by interfacing thin SrRuO 3 layers to Pr 0.7 Ca 0.3 MnO 3 , since it is known that the strong antiferromagnetic coupling between these two ferromagnets leads to complex magnetization states. Superlattices with sharp interfaces were grown by pulsed-laser deposition. The epitaxial interfacing with the Pr 0.7 Ca 0.3 MnO 3 layers led to major modifications of the structural symmetry of the SrRuO 3 layers. High resolution scanning transmission electron microscopy revealed that the individual SrRuO 3 layers of the superlattices had heterogeneous structure with varying oxygen octahedral tilt angles across the layers, turning their structure to be tetragonal-like, with largely suppressed octahedral tilts when the thickness of the neighboring Pr 0.7 Ca 0.3 MnO 3 layers was increased. These structural modifications were accompanied by major changes in the field dependence of the Hall signal with the mainly tetragonal SrRuO 3 layers showing features strongly reminiscent of a topological Hall effect. However, since there was an intimate link between Hall effect and structure, the Hall data were interpreted as arising from a superposition of Hall effect contributions from tetragonal and orthorhombic SrRuO 3 sub-layers.

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“…This spin chirality generates an effective electromagnetic field for electrons through the spin Berry phase mechanism. The resulting Hall effect, known as the Topological Hall (TH) effect, has been observed in perovskite oxides [9][10][11][12], chiral magnets [13,14], frustrated magnets [15], and Heusler alloys [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Topological Hall effect and emergent skyrmion crystal at manganite-iridate oxide interfaces

2019

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Scalar spin chirality is expected to induce a finite contribution to the Hall response at low temperatures. We study this spin-chirality-driven Hall effect, known as the topological Hall effect, at the manganite side of the interface between La1−xSrxMnO3 and SrIrO3. The ferromagnetic doubleexchange hopping at the manganite layer, in conjunction with the Dzyaloshinskii-Moriya (DM) interaction which arises at the interface due to broken inversion symmetry and strong spin-orbit coupling from the iridate layer, could produce a skyrmion-crystal (SkX) phase in the presence of an external magnetic field. Using the Monte Carlo technique and a two-orbital spin-fermion model for manganites, supplemented by an in-plane DM interaction, we obtain phase diagrams which reveal at low temperatures a clear SkX phase and also a low-field spin-spiral phase. Increasing temperature, a skyrmion-gas phase, precursor of the SkX phase upon cooling, was identified. The topological Hall effect primarily appears in the SkX phase, as observed before in oxide heterostructures. We conclude that the manganite-iridate superlattices provide another useful platform to explore a plethora of unconventional magnetic and transport properties. arXiv:1905.09887v2 [cond-mat.str-el]

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Ferroelectrically tunable magnetic skyrmions in ultrathin oxide heterostructures

Cited by 309 publications

References 52 publications

Coexistence of Surface and Bulk Ferromagnetism Mimics Skyrmion Hall Effect in a Topological Insulator

Coexistence of Surface and Bulk Ferromagnetism Mimics Skyrmion Hall Effect in a Topological Insulator

Unconventional anomalous Hall effect driven by oxygen-octahedra-tailoring of the SrRuO₃ structure

Topological Hall effect and emergent skyrmion crystal at manganite-iridate oxide interfaces

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Ferroelectrically tunable magnetic skyrmions in ultrathin oxide heterostructures

Cited by 309 publications

References 52 publications

Coexistence of Surface and Bulk Ferromagnetism Mimics Skyrmion Hall Effect in a Topological Insulator

Coexistence of Surface and Bulk Ferromagnetism Mimics Skyrmion Hall Effect in a Topological Insulator

Unconventional anomalous Hall effect driven by oxygen-octahedra-tailoring of the SrRuO3 structure

Topological Hall effect and emergent skyrmion crystal at manganite-iridate oxide interfaces

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Unconventional anomalous Hall effect driven by oxygen-octahedra-tailoring of the SrRuO₃ structure