Large Topological Hall Effect in a Short-Period Helimagnet MnGe

Kanazawa, Naoya; Onose, Y.; Arima, T.; Okuyama, Daisuke; Ohoyama, Kenji; Wakimoto, Shuichi; Kakurai, Kazuhisa; Ishiwata, Shintaro; Tokura, Y.

doi:10.1103/physrevlett.106.156603

Cited by 581 publications

(611 citation statements)

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“…This maximum value of the observed T xy  (~0.15cm) for MnNiGa is almost same as that for bulk MnGe (0.16 cm) [31] , which has a largest T xy  value among the bulk B20-type chiral magnets. The THE resistivity resulting from the fictitious magnetic field generated by the skyrmion spin textures can be approximated with nm with topological number of 2 [29] .…”

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confidence: 65%

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A Centrosymmetric Hexagonal Magnet with Superstable Biskyrmion Magnetic Nanodomains in a Wide Temperature Range of 100–340 K

et al. 2016

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Magnetic skyrmions are topologically protected vortex-like nanometric spin textures that have recently received growingly attention for their potential applications in future highperformance spintronic devices. Such unique mangetic naondomains have been recently discovered in bulk chiral magnetic materials, such as MnSi [1][2][3][4] , FeGe [5,6] , FeCoSi [7] , Cu 2 OSeO 3 [8][9][10] , -Mn-type Co-Zn-Mn [11] , and also GaV 4 S 8[12] a polar magnet. The crystal structure of these materials is cubic and lack of centrosymmetry, leading to the existence of Dzyaloshinskii-Moriya (DM) interactions. Unlike the conventional spin configurations, such as helical or conical, that are usually found in chiral magnets, a magnetic skyrmion has a particle-like swirling-spin configuration characterized by a topological index called the skyrmion number [13,14] . The nontrivial topology of magnetic skyrmions results in a number of

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confidence: 65%

“…including Refs. [1][2][3][4][5][6][7][8][9][10][11][12], [22], [29][30][31], [33]. The red solid squares indicate the experimental data based on the in-situ Lorentz TEM observations.…”

Section: Supporting Informationmentioning

confidence: 99%

A Centrosymmetric Hexagonal Magnet with Superstable Biskyrmion Magnetic Nanodomains in a Wide Temperature Range of 100–340 K

et al. 2016

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“…Once the considerations above are extended to three dimensions, one can define another topological spin texture called an emergent magnetic monopole [60][61][62] , which can act as a source or sink of a skyrmion string in three dimensions.…”

Section: Berry Phase Engineeringmentioning

confidence: 99%

Emergent functions of quantum materials

2017

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Materials can harbour quantum many-body systems, most typically in the form of strongly correlated electrons in solids, that lead to novel and remarkable functions thanks to emergence-collective behaviours that arise from strong interactions among the elements. These include the Mott transition, high-temperature superconductivity, topological superconductivity, colossal magnetoresistance, giant magnetoelectric e ect, and topological insulators. These phenomena will probably be crucial for developing the next-generation quantum technologies that will meet the urgent technological demands for achieving a sustainable and safe society. Dissipationless electronics using topological currents and quantum spins, energy harvesting such as photovoltaics and thermoelectrics, and secure quantum computing and communication are the three major fields of applications working towards this goal. Here, we review the basic principles and the current status of the emergent phenomena and functions in materials from the viewpoint of strong correlation and topology.E mergence is a concept developed for many-body systems, indicating the properties, phenomena, and functions that never appear in the individual elements but are realized only when a huge number of elements get together 1 . Inside materials, emergent phenomena are often seen due to the interaction of electronic states; with recent developments on electronic states in solids schematically summarized in Fig. 1a. Electrons in solids have several degrees of freedom: charge, spin and orbital, and are characterized by the topological nature determined by the atomic potential on the crystal lattice structure, as schematically shown in Fig. 1b. These five attributes are coupled together and determine the overall responses to stimuli, which appear as materials' electrical, magnetic, optical, thermal, and mechanical properties.These collective electrons demonstrate various macroscopic quantum phenomena, the representative example of which is superconductivity. One of the big challenges in condensed matter physics is to increase the temperature (T c ) at which superconductivity can be observed to above room temperature. However, there are many other macroscopic quantum phenomena that are already observable above room temperature. One is magnetism (by the Bohr-van Leeuwen theorem), and the other is ferroelectricity 2,3 . Remarkably, there are common features of these three macroscopic quantum phenomena: the order parameter, which is of quantum origin, behaves as a classical quantity, and the quantum topology plays a crucial role.The topological nature of the electronic states is the key concept in the most recent developments in understanding quantum materials. The quantum Hall effect, topological insulators, and topological superconductors are all characterized by nontrivial topologies in Hilbert space. The Berry phase, which describes the connection and curvature of the subspace of Hilbert space, plays the central role in the unified principle to describe this topological nature 4 . ...

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“…45) In MnGe, a unique three-dimensional spin structure has been observed. 46,47) The crystal symmetry of the B20 compounds is P2 1 3, and owing to its symmetry, the DM interaction should be given as D α µ = Dδ αµ . Figure 4(a) shows the DFT band structure of FeGe (black solid lines).…”

Section: Electronic Structure Of Fegementioning

confidence: 99%

“…In contrast, around MnGe, the DM interaction is very small while the experiments show a very small skyrmion size, indicating a large DM interaction. 46) This discrepancy may come from the validity of the evaluation using E(q) since this method assumes that the spatial spin variation is small. In contrast with other skyrmion materials like FeGe and MnSi, MnGe is proposed to have a unique three-dimensional skyrmion lattice structure, 47) For Fe 1−x Co x Ge, on the other hand, the values of J decrease with increasing x and almost vanish for x > 0.6, indicating that the ferromagnetic state becomes unstable.…”

Section: Electronic Structure Of Fegementioning

confidence: 99%

First-Principles Evaluation of the Dzyaloshinskii–Moriya Interaction

2018

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We review recent developments of formulations to calculate the Dzyaloshinskii-Moriya (DM) interaction from first principles. In particular, we focus on three approaches. The first one evaluates the energy change due to the spin twisting by directly calculating the helical spin structure. The second one employs the spin gauge field technique to perform the derivative expansion with respect to the magnetic moment. This gives a clear picture that the DM interaction can be represented as the spin current in the equilibrium within the first order of the spin-orbit couplings. The third one is the perturbation expansion with respect to the exchange couplings and can be understood as the extension of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction to the noncentrosymmetric spin-orbit systems. By calculating the DM interaction for the typical chiral ferromagnets Mn 1−x Fe x Ge and Fe 1−x Co x Ge, we discuss how these approaches work in actual systems.

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Large Topological Hall Effect in a Short-Period Helimagnet MnGe

Cited by 581 publications

References 28 publications

A Centrosymmetric Hexagonal Magnet with Superstable Biskyrmion Magnetic Nanodomains in a Wide Temperature Range of 100–340 K

A Centrosymmetric Hexagonal Magnet with Superstable Biskyrmion Magnetic Nanodomains in a Wide Temperature Range of 100–340 K

Emergent functions of quantum materials

First-Principles Evaluation of the Dzyaloshinskii–Moriya Interaction

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