Anomalous Hall effect derived from multiple Weyl nodes in high-mobility EuTiO
            <sub>3</sub>
            films

Takahashi, Kei; Ishizuka, Hiroaki; Murata, Tomoki; Wang, Hongtao; Tokura, Y.; Nagaosa, Naoto; Kawasaki, Masashi

doi:10.1126/sciadv.aar7880

Cited by 107 publications

(93 citation statements)

References 35 publications

(47 reference statements)

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“…The high temperature growth dramatically improves the crystalline quality of the films. As such, the carrier mobilities achieved this way are one order of magnitude higher than those of the previously reported thin films [ 25 ] grown at 900 °C on the mismatched substrate (LaAlO 3 ) 0.3 (Sr 2 AlTaO 6 ) 0.7 (LSAT), as shown in Figure 1f. The details of our thin film growth conditions and characterizations are provided in the Methods section, and the section “Structural analysis of the La‐doped EuTiO 3 samples” and Figure S2 (Supporting Information).…”

Section: Figurementioning

confidence: 62%

“…As shown in Figure 1f, the films epitaxially grown on SrTiO 3 at high temperatures (see the Methods section) satisfy this condition and become conducting once the La doping concentration reaches 1.4 × 10 18 cm −3 . In comparison, the previously reported EuTiO 3 films grown on an LSAT substrate at lower temperatures [ 25 ] as well as the reduced EuTiO 3 bulk crystals [ 26 ] require a much larger number of dopants to show conductance.…”

Section: Figurementioning

confidence: 86%

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Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO₃

et al. 2020

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Magnetic semiconductors are a vital component in the understanding of quantum transport phenomena. To explore such delicate, yet fundamentally important, effects, it is crucial to maintain a high carrier mobility in the presence of magnetic moments. In practice, however, magnetization often diminishes the carrier mobility. Here, it is shown that EuTiO3 is a rare example of a magnetic semiconductor that can be desirably grown using the molecular beam epitaxy to possess a high carrier mobility exceeding 3000 cm2 V−1 s−1 at 2 K, while intrinsically hosting a large magnetization value, 7 μB per formula unit. This is demonstrated by measuring the Shubnikov–de Haas (SdH) oscillations in the ferromagnetic state of EuTiO3 films with various carrier densities. Using first‐principles calculations, it is shown that the observed SdH oscillations originate genuinely from Ti 3d‐t2g states which are fully spin‐polarized due to their energetical proximity to the in‐gap Eu 4f bands. Such an exchange coupling is further shown to have a profound effect on the effective mass and fermiology of the Ti 3d‐t2g electrons, manifested by a directional anisotropy in the SdH oscillations. These findings suggest that EuTiO3 film is an ideal magnetic semiconductor, offering a fertile field to explore quantum phenomena suitable for spintronic applications.

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Section: Figurementioning

confidence: 62%

Section: Figurementioning

confidence: 86%

Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO₃

et al. 2020

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“…Both AHE and AMR can serve as signatures of such interactions [13][14][15].Degenerately doped, antiferromagnetic EuTiO 3 is an interesting testbed for these ideas for several reasons. Despite a small net magnetization, it exhibits an intrinsic AHE that changes sign as a function of the carrier density [16][17][18]. This is indicative of the Fermi level being located near a Weyl point or an avoided crossing, which are sources of Berry curvature [5,7].…”

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confidence: 99%

“…Additionally, the Zeeman splitting of the bands can be large in EuTiO 3 . While not captured in zero-field DFT calculations shown in the Supplementary Information, Zeeman fields have been suggested as a mechanism to move existing Weyl points in the Brillouin zone [18] or even generate new ones [30]. While this may be reflected in the AHE [17,18], studies of the AMR effect can provide more direct information about the Fermi surface symmetry [13] and changes under magnetic fields.…”

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Anisotropic magnetoresistance in the itinerant antiferromagnetic EuTiO3

Ahadi

Salmani-Rezaie

et al. 2019

Phys. Rev. B

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We report on measurements of the anisotropic magnetoresistance (AMR) of doped EuTiO 3 . It is shown that the primary contribution to the AMR is the crystalline component, which depends on the relative orientation between the magnetic moments and the crystal axes. With increasing magnetic field, a four-fold crystalline AMR undergoes a change in its alignment with respect to the crystal axes. The results are discussed in the context the coupling between spin canting, electronic structure, and transport. We discuss the potential role of Weyl points in the band structure. At high fields, the AMR transitions to uniaxial symmetry, which is lower than that of the lattice, along with a cross-over from positive to negative magnetoresistance.3 Spin-orbit coupling plays a central role in the anisotropic magnetoresistance (AMR) and anomalous Hall effect (AHE) [1] of itinerant ferromagnets and in materials with topologically non-trivial electronic states. While an elegant theoretical framework exists for the intrinsic AHE and its connection to the Berry curvature of the electronic bands [2-7], AMR remains comparatively less well understood. Recently, both AMR and AHE have also attracted significant attention in antiferromagnetic metals and semiconductors [8,9]. For example, significant AHEs in non-collinear antiferromagnets have been discovered [10][11][12]. Another phenomenon of recent interest is the potential coupling between the orientation of the Néel vector and the topology of the electronic states in antiferromagnets with symmetry-protected Dirac and/or Weyl points in their band structure [13,14]. Both AHE and AMR can serve as signatures of such interactions [13][14][15].Degenerately doped, antiferromagnetic EuTiO 3 is an interesting testbed for these ideas for several reasons. Despite a small net magnetization, it exhibits an intrinsic AHE that changes sign as a function of the carrier density [16][17][18]. This is indicative of the Fermi level being located near a Weyl point or an avoided crossing, which are sources of Berry curvature [5,7]. Recent density functional calculations (DFT) show the presence of Weyl points, which are near the Fermi level for the doping concentration where the sign changes in the AHE are observed, in case of ferromagnetic order [17]. At zero applied fields, the Eu moments order antiferromagnetically (G-type) [19, 20] with a Néel temperature of ~6 K that is relatively insensitive to the amount of doping [17]. A collinear spin arrangement cannot give rise to Weyl points, because time reversal and inversion symmetry are both present. This can also be seen in DFT calculations (see Supplementary Information [21]). Under applied magnetic fields, however, the spins cant and produce a small net magnetization [17]. The Eu spin orientation can

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“…This enhanced AHE compared with the magnetization can be understood as the shifts of the Weyl points due to the tilting of the spins in AIAO state [9]. The crucial role of Weyl fermions in AHE has been revealed also in semiconductor EuTiO 3 [10].…”

Section: Various Weyl Semimetallic Phases In Pyrochlore Oxidesmentioning

confidence: 99%

Correlated Weyl Fermions in Oxides

Nagaosa

2020

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019)

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Anomalous Hall effect derived from multiple Weyl nodes in high-mobility EuTiO ₃ films

Abstract: We report a nonmonotonic magnetic field dependence of the anomalous Hall effect due to the change of the Zeeman splitting.

Cited by 107 publications

References 35 publications

Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO₃

Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO₃

Anisotropic magnetoresistance in the itinerant antiferromagnetic EuTiO3

Correlated Weyl Fermions in Oxides

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Anomalous Hall effect derived from multiple Weyl nodes in high-mobility EuTiO 3 films

Abstract: We report a nonmonotonic magnetic field dependence of the anomalous Hall effect due to the change of the Zeeman splitting.

Cited by 107 publications

References 35 publications

Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO3

Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO3

Anisotropic magnetoresistance in the itinerant antiferromagnetic EuTiO3

Correlated Weyl Fermions in Oxides

Contact Info

Product

Resources

About

Anomalous Hall effect derived from multiple Weyl nodes in high-mobility EuTiO ₃ films

Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO₃

Anisotropic Quantum Transport through a Single Spin Channel in the Magnetic Semiconductor EuTiO₃