Anomalous transport due to Weyl fermions in the chiral antiferromagnets Mn3X, X = Sn, Ge

Chen, Taishi; Tomita, Takahiro; Minami, Susumu; Fu, Morgan; Koretsune, Takashi; Kitatani, Motoharu; Ikhlas, Muhammad; Nishio–Hamane, Daisuke; Ishii, Ryuji; Ishii, Fumiyuki; Arita, Ryotaro; Nakatsuji, Satoru

doi:10.1038/s41467-020-20838-1

Cited by 134 publications

(107 citation statements)

References 94 publications

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“…Thus, the source of the Berry curvature must be near the Fermi energy and in this case the Weyl points, as discussed in Section 3.3. Furthermore, experiments on two crystals with different compositions were quantitatively consistent with calculations performed by first-principles calculations, again confirming the effect of Berry curvature due to the Weyl fermions as the source of the large fictitious magnetic field (30). The ANE was found useful for imaging the magnetic domains by taking advantage of a laser-induced local thermal gradient (109).…”

Section: Large Anomalous Nernst Effect and Berry Curvature Due To Weyl Fermionssupporting

confidence: 57%

“…Strikingly, the ANE in Mn 3 Sn is found to be more than 100 times larger than the estimate derived from its magnetization, on par with the highest value measured for an FM metal (Figure 1b; 35,67). The large Nernst effect has been also found in Mn 3 Ge (30,108).…”

Section: Large Anomalous Nernst Effect and Berry Curvature Due To Weyl Fermionsmentioning

confidence: 63%

“…Since their discovery in ferromagnets in the nineteenth century, both AHEs and ANEs have been known to be proportional to magnetization. In fact, as summarized in Figure 1, AHE and ANE of a number of ferromagnets are found to grow roughly linearly with magnetization (30). In contrast, the topological magnets such as Mn 3 Sn and Co 2 MnGa show much larger AHE and ANE than those expected based on the scaling law (9,11,35).…”

Section: Berry Curvature In Momentum Spacementioning

confidence: 87%

“…This anisotropic magnetoconductivity is found evident also in the field angle dependent measurements. In sharp contrast with LMC due to spin fluctuations, the magnitude of the observed positive LMC for E B rises and the anisotropy of the LMC becomes more pronounced in Mn 3 Sn on cooling from 300 K down to 60 K. The observed large, strongly anisotropic LMC in a magnet is unprecedented, providing strong evidence for the chiral anomaly originating from the Weyl fermions (30). In addition, the temperature dependence of the thermal Hall conductivity and its comparison with AHC confirms the intrinsic Berry curvature mechanism of the transverse transport and the dominant contribution from Weyl fermions (30,67,(105)(106)(107).…”

Section: Evidence For Weyl Fermionsmentioning

confidence: 89%

“…Instead, we first cover the general properties of topological magnets. A hallmark of such properties is the anomalous Hall effect (AHE) in an antiferromagnetic (AF) Weyl semimetal (9,10,(28)(29)(30). The discovery of the large spontaneous AHE is significant as it alters the pessimistic view of antiferromagnets being useless for practical applications.…”

Section: Introductionmentioning

confidence: 99%

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Topological Magnets: Functions Based on Berry Phase and Multipoles

Nakatsuji

Arita

2022

Annu. Rev. Condens. Matter Phys.

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Macroscopic responses of magnets are often governed by magnetization and, thus, have been restricted to ferromagnets. However, such responses are strikingly large in the newly developed topological magnets, breaking the conventional scaling with magnetization. Taking the recently discovered antiferromagnetic (AF) Weyl semimetals as a prime example, we highlight the two central ingredients driving the significant macroscopic responses: the Berry curvature enhanced because of nontrivial band topology in momentum space, and the cluster magnetic multipoles in real space. The combination of large Berry curvature and multipole enables large macroscopic responses such as the anomalous Hall and Nernst effects, the magneto-optical effect, and the novel magnetic spin Hall effect in antiferromagnets with negligible net magnetization, but also allows us to manipulate these effects by electrical means. Furthermore, nodal-point and nodal-line semimetallic states in ferromagnets may provide the strongly enhanced Berry curvature near the Fermi energy, leading to large responses beyond the conventional magnetization scaling. These significant properties and functions of the topological magnets lay the foundation for future technological development such as spintronics and thermoelectric technology. Expected final online publication date for the Annual Review of Condensed Matter Physics, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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Section: Large Anomalous Nernst Effect and Berry Curvature Due To Weyl Fermionssupporting

confidence: 57%

Section: Large Anomalous Nernst Effect and Berry Curvature Due To Weyl Fermionsmentioning

confidence: 63%

Section: Berry Curvature In Momentum Spacementioning

confidence: 87%

Section: Evidence For Weyl Fermionsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Topological Magnets: Functions Based on Berry Phase and Multipoles

Nakatsuji

Arita

2022

Annu. Rev. Condens. Matter Phys.

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Giant and Robust Anomalous Nernst Effect in a Polycrystalline Topological Ferromagnet at Room Temperature

Feng

Minami

Akamatsu

et al. 2022

Adv Funct Materials

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Recent discoveries of the topological magnets have opened a new path for developing a much simpler thermoelectric conversion module using the anomalous Nernst effect (ANE). To accelerate such innovation, it is essential to design materials suitable for industrial processes, and thus a high‐ANE polycrystalline material has been highly desired. Recently, the giant room‐temperature ANE has been reported in single crystals of the topological ferromagnet Fe3Ga. Owning to its cubic structure, the anomalous Hall effect and ANE are isotropic. These properties potentially allow to employ a polycrystalline form of the material to design an ANE‐based thermopile. Here, a giant and robust room‐temperature ANE in the polycrystalline FexGa4−x (2.96 < x < 3.15) is reported, which can be enhanced up to 5.4 µV K−1; this value hits the highest room‐temperature record for polycrystalline magnets. Comparison of the experimental results with the theoretical study of the Fe‐doping effect on the transport properties of FexGa4−x reveals that the Fermi energy tuning near the topological nodal‐web structure is the key to enhancing the ANE. Moreover, the large value of more than 5.1 µV K−1 is observed for an extended region of composition, confirming the robust characteristics of the topological electronic structure.

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Large Anomalous Hall Effect at Room Temperature in a Fermi‐Level‐Tuned Kagome Antiferromagnet

Song,

Zhou,

et al. 2024

Adv Funct Materials

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The recent discoveries of surprisingly large anomalous Hall effect (AHE) in antiferromagnets have attracted much attention due to their promising use in spintronics devices. However, such AHE‐hosting antiferromagnetic materials are rare in nature. Herein, it is demonstrated that Mn2.4Ga, a Fermi‐level‐tuned kagome antiferromagnet, has a large anomalous Hall conductivity of ≈150 Ω−1 cm−1 at room temperature that surpasses the usual high values (i.e., 20–50 Ω−1 cm−1) observed so far in two outstanding kagome antiferromagnets, Mn3Sn and Mn3Ge. Although the triangular spin structure of Mn2.4Ga shows a weak net magnetic moment of ≈0.05 µB per formula unit, it guarantees a nonzero Berry curvature in the kagome plane. Moreover, the anomalous Hall conductivity exhibits a sign reversal with the rotation of a small magnetic field that can be ascribed to the field‐controlled chirality of the spin triangular structure. This theoretical calculations further suggest that the large AHE in Mn2.4Ga originates from a significantly enhanced Berry curvature associated with the tuning of the Fermi level close to the Weyl points. These properties, together with the ability to manipulate moment orientations using a moderate external magnetic field, make Mn2.4Ga extremely exciting for future antiferromagnetic spintronics.

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Anomalous transport due to Weyl fermions in the chiral antiferromagnets Mn3X, X = Sn, Ge

Cited by 134 publications

References 94 publications

Topological Magnets: Functions Based on Berry Phase and Multipoles

Topological Magnets: Functions Based on Berry Phase and Multipoles

Giant and Robust Anomalous Nernst Effect in a Polycrystalline Topological Ferromagnet at Room Temperature

Large Anomalous Hall Effect at Room Temperature in a Fermi‐Level‐Tuned Kagome Antiferromagnet

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