Abstract
The kagome lattice Co
3
Sn
2
S
2
exhibits the quintessential topological phenomena of a magnetic Weyl semimetal such as the chiral anomaly and Fermi-arc surface states. Probing its magnetic ...properties is crucial for understanding this correlated topological state. Here, using spin-polarized scanning tunneling microscopy/spectroscopy (STM/S) and non-contact atomic force microscopy (nc-AFM) combined with first-principle calculations, we report the discovery of localized spin-orbit polarons (SOPs) with three-fold rotation symmetry nucleated around single S-vacancies in Co
3
Sn
2
S
2.
The SOPs carry a magnetic moment and a large diamagnetic orbital magnetization of a possible topological origin associated relating to the diamagnetic circulating current around the S-vacancy. Appreciable magneto-elastic coupling of the SOP is detected by nc-AFM and STM. Our findings suggest that the SOPs can enhance magnetism and more robust time-reversal-symmetry-breaking topological phenomena. Controlled engineering of the SOPs may pave the way toward practical applications in functional quantum devices.
Topological materials are expected to show distinct transport signatures owing to their unique band-inversion characteristic and band-crossing points. However, the intentional modulation of such ...topological responses through experimentally feasible means has yet to be explored in depth. Here, an unusual elevation of the anomalous Hall effect (AHE) is obtained in electron (Ni)-doped magnetic Weyl semimetals Co3−xNixSn2S2, showing peak values in the anomalous Hall-conductivity, Hall-angle, and Hall-factor at a relatively low doping level of x = 0.11 . The separation of intrinsic and extrinsic contributions using the TYJ scaling model indicates that such a significant enhancement is dominated by the intrinsic mechanism of the electronic Berry curvature. Theoretical calculations reveal that compared with the Fermi-level shifting from electron filling, a usually overlooked effect of doping, that is, local disorder, imposes a striking effect on broadening of the bands and narrowing of the inverted gap, thus resulting in an elevation of the integrated Berry curvature. Our results not only realize an enhancement of the AHE in a magnetic Weyl semimetal, but also provide a practical design principle for modulating the bands and transport properties in topological materials by exploiting the local disorder effect from doping.
The promise of topologically vortex‐like magnetic spin textures hinges on the intriguing physical properties and theories in fundamental research and their distinguished roles as high‐efficiency ...information units in future spintronics. The exploration of such magnetic states with unique spin configurations has never ceased. In this study, the emergence of unconventional (anti)meron chains from a domain wall pair is directly observed at zero field in 2D ferromagnetic Fe5−xGeTe2, closely correlated with significant enhancement of the in‐plane magnetization and weak van der Waals interactions. The simultaneous appearance of a large topological Hall effect is observed at the same temperature range as that of the abnormal magnetic transition. Moreover, the distinctive features of the (anti)meron chains and their collective dynamic behavior under external fields may provide concrete experimental evidence for the recent theoretical prediction of the magnetic‐domain‐wall topology and endorse a broader range of possibilities for electronics, spintronics, condensed matter physics, etc.
The generation of (anti)meron chains from conventional domain walls is directly observed at zero field in 2D ferromagnetic Fe5−xGeTe2, which closely correlates with the weak van der Waals interaction and temperature‐dependent spin anisotropy transformation. The simultaneous topological Hall effect and the collectively dynamic behavior of the (anti)meron chains under external fields experimentally highlight the theoretical prediction of magnetic‐domain‐wall topology.
The anomalous Hall effect (AHE) can be induced by intrinsic mechanisms due to the band Berry phase and extrinsic one arising from the impurity scattering. The recently discovered magnetic Weyl ...semimetal Co3Sn2S2 exhibits a large intrinsic anomalous Hall conductivity (AHC) and a giant anomalous Hall angle (AHA). The predicted energy dependence of the AHC in this material exhibits a plateau at 1000 Ω−1 cm−1 and an energy width of 100 meV just below EF, thereby implying that the large intrinsic AHC will not significantly change against small‐scale energy disturbances such as slight p‐doping. Here, the extrinsic contribution is successfully triggered from alien‐atom scattering in addition to the intrinsic one of the pristine material by introducing a small amount of Fe dopant to substitute Co in Co3Sn2S2. The experimental results show that the AHC and AHA can be prominently enhanced up to 1850 Ω−1 cm−1 and 33%, respectively, owing to the synergistic contributions from the intrinsic and extrinsic mechanisms as distinguished by the TYJ model. In particular, the tuned AHA exhibits a record value among known magnetic materials in low fields. This study opens up a pathway to engineer giant AHE in magnetic Weyl semimetals, thereby potentially advancing the topological spintronics/Weyltronics.
Due to the prominent contribution of both the intrinsic and extrinsic Hall mechanisms, significantly enhanced AHC (≈1850 Ω−1 cm−1) and AHA (≈33%) are obtained at the zero field in the magnetic Weyl semimetal Co3Sn2S2 by controlling slight Fe doping. In comparison with other AHE materials, the AHC and AHA for Co3–xFexSn2S2 exhibit record values, which can greatly benefit Weyltronics applications.
Abstract
Exploring and controlling topological textures such as merons and skyrmions has attracted enormous interests from the perspective of fundamental research and spintronic applications. It has ...been predicted theoretically and proved experimentally that the lattice form of topological meron-skyrmion transformation can be realized with the requirement of external magnetic fields in chiral ferromagnets. However, such topological transition behavior has yet to be verified in other materials. Here, we report real-space observation of magnetic topology transformation between meron pairs and skyrmions in the localized domain wall of ferrimagnetic GdFeCo films without the need of magnetic fields. The topological transformation in the domain wall of ferrimagnet is introduced by temperature-induced spin reorientation transition (SRT) and the underlying mechanism is revealed by micromagnetic simulations. The convenient electric-controlling topology transformation and driving motion along the confined domain wall is further anticipated, which will enable advanced application in magnetic devices.
Grouping different transition metal oxides together by interface engineering is an important route toward emergent phenomenon. While most of the previous works focused on the interface effects in ...perovskite/perovskite heterostructures, here we reported on a symmetry mismatch-driven spin reorientation toward perpendicular magnetic anisotropy in perovskite/brownmillerite heterostructures, which is scarcely seen in tensile perovskite/perovskite heterostructures. We show that alternately stacking perovskite La
Sr
MnO
and brownmillerite LaCoO
causes a strong interface reconstruction due to symmetry discontinuity at interface: neighboring MnO
octahedra and CoO
tetrahedra at the perovskite/brownmillerite interface cooperatively relax in a manner that is unavailable for perovskite/perovskite interface, leading to distinct orbital reconstructions and thus the perpendicular magnetic anisotropy. Moreover, the perpendicular magnetic anisotropy is robust, with an anisotropy constant two orders of magnitude greater than the in-plane anisotropy of the perovskite/perovskite interface. The present work demonstrates the great potential of symmetry engineering in designing artificial materials on demand.
Large rotating magnetocaloric effect (MCE) has been observed in some single crystals due to strong magnetocrystalline anisotropy. By utilizing the rotating MCE, a new type of rotary magnetic ...refrigerator can be constructed, which could be more simplified and efficient than the conventional one. However, compared with polycrystalline materials, the high cost and complexity of preparation for single crystals hinder the development of this novel magnetic refrigeration technology. For the first time, here we observe giant rotating MCE in textured DyNiSi polycrystalline material, which is larger than those of most rotating magnetic refrigerants reported so far. This result suggests that DyNiSi compound could be attractive candidate of magnetic refrigerants for novel rotary magnetic refrigerator. By considering the influence of demagnetization effect on MCE, the origin of large rotating MCE in textured DyNiSi is attributed to the coexistence of strong magnetocrystalline anisotropy and highly preferred orientation. Our study on textured DyNiSi not only provides a new magnetic refrigerant with large rotating MCE for low temperature magnetic refrigeration, but also opens a new way to exploit magnetic refrigeration materials with large rotating MCE, which will be highly beneficial to the development of rotating magnetic refrigeration technology.
The conductance confined at the interface of complex oxide heterostructures provides new opportunities to explore nanoelectronic as well as nanoionic devices. Herein we show that metallic interfaces ...can be realized in SrTiO3-based heterostructures with various insulating overlayers of amorphous LaAlO3, SrTiO3, and yttria-stabilized zirconia films. On the other hand, samples of amorphous La7/8Sr1/8MnO3 films on SrTiO3 substrates remain insulating. The interfacial conductivity results from the formation of oxygen vacancies near the interface, suggesting that the redox reactions on the surface of SrTiO3 substrates play an important role.
Magnetic skyrmions, particular those without the support of external magnetic fields over a wide temperature region, are promising as alternative spintronic units to overcome the fundamental size ...limitation of conventional magnetic bits. In this study, we use in situ Lorentz microscope to directly demonstrate the generation and sustainability of robust biskyrmion lattice at zero magnetic field over a wide temperature range of 16–338 K in MnNiGa alloy. This procedure includes a simple field-cooling manipulation from 360 K (higher than Curie temperature T C ∼ 350 K), where topological transition easily occurs by adapting the short-range magnetic clusters under a certain magnetic field. The biskyrmion phase is favored upon cooling below T C. Once they are generated, the robust high-density biskyrmions persist even after removing the external magnetic field due to the topological protection and the increased energy barrier.
Particle‐like magnetic textures with nanometric sizes, such as skyrmions, are potentially suitable for designing high‐efficiency information bits in future spintronics devices. In general, the ...Dzyaloshinskii–Moriya interactions and dipolar interactions are the dominant factors for generating nonlinear spin configurations. However, to stabilize the topological skyrmions, an external magnetic field is usually required. In this study, the spontaneous emergence of skyrmions is directly observed, together with the unique successive topological domain evolution during the spin reorientation transition in a neodymium–cobalt (NdCo5) rare‐earth magnet. On decreasing the temperature, nanometric skyrmion lattices evolve into enclosed in‐plane domains (EIPDs) similar to mini bar‐magnets with size below 120 nm. The internal magnetization rotates with magnetic anisotropy, demonstrating the ability to manipulate the mini bar‐magnets. The nanoscale EIPD lattices remain robust over the wide temperature range of 241–167 K, indicating the possibility of high‐density in‐plane magnetic information storage. The generation of spontaneous magnetic skyrmions and the successive domain transformation in the traditional NdCo5 rare‐earth magnet may prompt application exploration for topological magnetic spin textures with novel physical mechanisms in versatile magnets.
Spontaneous magnetic biskyrmion lattices and the successive transformation into enclosed in‐plane domains over a broad temperature range of 120–282 K is directly observed by in situ cooling a hexagonal rare‐earth NdCo5 alloy in Lorentz TEM. The ability to manipulate topological magnetization by anisotropy invites application exploration of novel topological magnetic spin textures and physical mechanisms in rare‐earth magnets.
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