Distinguishing the Two-Component Anomalous Hall Effect from the Topological Hall Effect

Abstract

In transport, the topological Hall effect (THE) presents itself as nonmonotonic features (or humps and dips) in the Hall signal and is widely interpreted as a sign of chiral spin textures, like magnetic skyrmions. However, when the anomalous Hall effect (AHE) is also present, the coexistence of two AHEs could give rise to similar artifacts, making it difficult to distinguish between genuine THE with AHE and two-component AHE. Here, we confirm genuine THE with AHE by means of transport and magneto-optical Kerr effect (MOKE) microscopy, in which magnetic skyrmions are directly observed, and find that genuine THE occurs in the transition region of the AHE. In sharp contrast, the artifact “THE” or two-component AHE occurs well beyond the saturation of the “AHE component” (under the false assumption of THE + AHE). Furthermore, we distinguish artifact “THE” from genuine THE by three methods: (1) minor loops, (2) temperature dependence, and (3) gate dependence. Minor loops of genuine THE with AHE are always within the full loop, while minor loops of the artifact “THE” may reveal a single loop that cannot fit into the “AHE component”. In addition, the temperature or gate dependence of the artifact “THE” may also be accompanied by a polarity change of the “AHE component”, as the nonmonotonic features vanish, while the temperature dependence of genuine THE with AHE reveals no such change. Our work may help future researchers to exercise caution and use these methods for careful examination in order to ascertain the genuine THE.

Néel Skyrmion Bubbles in La0.7Sr0.3Mn1–xRuxO3 Multilayers

“…We mention that our Hall resistance investigations of a single 5% Ru-LSMO layer (42.5 nm thick) grown on LSAT(100) under the same conditions as the multilayer did not exhibit humps of the Hall loops, at any temperature from 10 to 200 K, and the magnetic domain imaging by MFM showed no evidence of Néel skyrmion bubbles . THE contributions may not manifest as pronounced humps necessarily, but rather as dip and hump minute modulations of the Hall loops, , similar to how our Hall loops behave, especially at high temperatures (see Figure S4). The Hall loops agree very well with perpendicular magnetization loops measured by SQUID magnetometry (see Figure S5).…”

Visualizing the interplay of Dirac mass gap and magnetism at nanoscale in intrinsic magnetic topological insulators

“…A large density of Bi Mn antisites can also be inferred from the heavily degenerate n-type nature of the material. Considering the disorder effect, it is understandable why the QAH effect is not universally observed in an odd-SL MnBi 2 Te 4 thin film ( 16 , 17 , 19 , 20 , 46 ).…”

“…Indeed, the QAH effect has been observed in MnBi 2 Te 4 at a significantly higher temperature of 1.4 K ( 15 ). However, the QAH effect is not always observed, even in samples that appear similar ( 16 – 20 ). Moreover, observations of the Dirac mass gap, a prerequisite for the QAH effect and a direct consequence of exchange coupling between the Dirac surface state and the spontaneous magnetization ( 21 , 22 ), has proven to be challenging and remained unclear ( 9 , 23 – 30 ).…”

“…Besides, defects distribution inhomogeneity can complicate the magnetic order ( 30 – 32 ) and impact the exchange-gap distribution ( 6 , 32 – 37 ). Spatial fluctuations of chemical potential and another chemical composition mixing, such as Bi 2 Te 3 and MnTe 2 ( 16 , 17 , 38 ), further entangle the electronic structure and complicate the gap observation. Thus, to properly address the nature of Dirac mass gap, a microscopic characterization based on intrinsic samples with Fermi level lying within the Dirac gap is crucial.…”

Probing a Proximity-Coupling-Induced Hybrid Anomalous Hall Effect in Epitaxial MnBi2Te4/Bi2Te3 Nanostructures

“…There is a representative Hall trace in 4SL MnBi 2 Te 4 , which should exhibit antiferromagnetic properties theoretically. In order to further elucidate the relevant mechanism, we decompose the typical Hall loop by a classical molecular field model, and the related equation can be expressed as follows …”