Emerging from the intricate interplay of topology and magnetism, the giant anomalous Hall effect (AHE) is the most known topological property of the recently discovered kagomé ferromagnetic Weyl semimetal Co3Sn2S2 with the magnetic Co atoms arranged on a kagomé lattice. Here it is reported that the AHE in Co3Sn2S2 can be fine-tuned by an applied magnetic field orientated within ≈2° of the kagomé plane, while beyond this regime, it stays unchanged. Particularly, it can vanish in magnetic fields parallel to the kagomé plane and even decrease in magnetic fields collinear with the spin direction. This tunable AHE can be attributed to local spin switching enabled by the geometrical frustration of the magnetic kagomé lattice, revealing that spins in a kagomé ferromagnet change their switching behavior as the magnetic field approaches the kagomé plane. These results also suggest a versatile way to tune the properties of a kagomé magnet.

Kagome system usually attracts great interest in condensed matter physics due to its unique structure hosting various exotic states such as superconductivity (SC), charge density wave (CDW), and nontrivial topological states. Topological semimetal RbTi3Bi5 consisting of the kagome layer of Ti shares a similar crystal structure to topological correlated materials AV3Sb5 (A = K, Rb, Cs) but with the absence of CDW and SC. Systematic de Haas-van Alphen (dHvA) oscillation measurements are performed on the single crystals of RbTi3Bi5 to pursue nontrivial topological physics and exotic states. Combining with theoretical calculations, detailed Fermi surface topology and band structure are investigated. A two-dimensional (2D) Fermi pocket \b{eta} is revealed with a light-effective mass in consistent with the semimetal predictions. Landau Fan of RbTi3Bi5 reveals a zero Berry phase for the \b{eta} oscillation in contrast to that of CsTi3Bi5. These results suggest the kagome RbTi3Bi5 is a good candidate to explore nontrivial topological exotic states and topological correlated physics.

Systemically angular and planar transport investigations are performed in layered antiferromagnetic (AF) V5S8. In this AF system, obvious anomalous Hall effect (AHE) is observed with a large Hall angle of 0.1 compared to that in ferromagnetic (FM) system. It can persist to the temperatures above AF transition and exhibit strong angular field dependence. The phase diagram reveals various magnetic states by rotating the applied field. By analyzing the anisotropic transport behavior, magnon contributions are revealed and exhibit obvious angular dependence with a spin-flop vanishing line. The observed prominent planar Hall effect and anisotropic magnetoresisitivity exhibit two-fold systematical angular dependent oscillations. These behaviors are attributed to the scattering from spin-orbital coupling instead of nontrivial topological origin. Our results reveal anisotropic interactions of magnetism and electron in V5S8, suggesting potential opportunities for the AF spintronic sensor and devices.

Elemental Tellurium (Te) is an important p ‐type semiconductor with wide practical applications. It is currently of great interest as a chiral crystal with broken inversion and mirror symmetries, and its topological nature is under active discussion. Here the Shubnikov–de Haas (SdH) oscillations with a nontrivial π Berry phase and the quantum linear magnetoresistance (MR) in as‐synthesized high‐mobility Te single crystals are reported. The vapor transport grown Te shows a hollow hexagonal prism structure with tunable carrier density and high mobility of about 1000 cm 2 V −1 s −1 at low temperature. For concentration p > 10 17 cm −3 , the conspicuous SdH oscillations map out the dumbbell‐shaped Fermi surface and the long‐standing peculiar amplitude change with varying magnetic field orientation is explained by careful quantitative analyses. Pulsed magnetic field measurements up to 57 T disclose a quantum linear MR beyond the quantum limit and the Landau fan diagram clearly reveals a topologically nontrivial π Berry phase. This work paves way for the synthesis of high‐mobility Te structures and sheds light onto the intrinsic nontrivial topology of the attractive elemental substance.

Exploration of exotic transport behavior for quantum materials is of great interest and importance for revealing exotic orders to bring new physics. In this work, we report the observation of unconventional prominent planar Hall effect (PHE) and planar anisotropic magnetoresistivity (PAMR) in strange kagome metal KV 3 Sb 5 . The PHE and PAMR, which are driven by an in-plane magnetic field and display sharp difference from other Hall effects driven by an out-of-plane magnetic field or magnetization, exhibit exotic higher-order oscillations in sharp contrast to those following empirical rule only allowing two-fold symmetrical oscillations. These higher-order oscillations exhibit strong field and temperature dependence and vanish around charge density wave (CDW) transition. The unique transport properties suggest a significant interplay of the lattice, magnetic and electronic structure in KV 3 Sb 5 . This interplay can couple the hidden anisotropy and transport electrons leading to the unconventional PHE and PAMR in contrast to other materials.

Short-range (SR) magnetic orders such as magnetic glass orders or fluctuations in a quantum system usually host exotic states or critical behaviors. As the long-range (LR) magnetic orders, SR magnetic orders can also break time-reversal symmetry and drive the non-zero Berry curvature leading to novel transport properties. In this work, we report that in EuZn$_2$As$_2$ compound, besides the LR A-type antiferromagnetic (AF) order, the SR magnetic order is observed in a wide temperature region. The magnetization measurements and electron spin resonance (ESR) measurements reveal the ferromagnetic (FM) correlations for this SR magnetic order which results in an obvious anomalous Hall effect above the AF transition. Moreover the ESR results reveal that this FM SR order coexists with LR AF order exhibiting anisotropic magnetic correlations below the AF transition. The interactions of LR and SR magnetism evolving with temperature and field can host non-zero spin charility and berry curvature leading the additional topological Hall contribution even in a centrosymmetric simple AF system. Our results indicate that EuZn$_2$As$_2$ is a fertile platform to investigate exotic magnetic and electronic states.

Layered transition-metal dichalcogenide HfTe2 is a topological semimetal candidate attracting increasing attention recently. The map of the Fermi surface is of interest and importance to understand its properties. Here, we present a study of Shubnikov-de Haas (SdH) oscillations and planar Hall effect (PHE) in HfTe2. The single crystals grown by flux method show the largest unsaturated magnetoresistance (MR) effect of 1.1x104% at 14 T and 2 K. The angle-resolved SdH oscillations reveal that the Fermi surface consists of three pockets with different anisotropy. In addition, we observe PHE and anisotropic MR effect in the material for a wide temperature range. The effective mass, carrier density, and quantum transport mobility are quantified in the system, and the Berry phase is discussed. Our work provides crucial insights into the electronic structure and the Fermi surface of the semimetal.

Magnetism plays a key role in the emergence of topological phenomena in the Weyl semimetal Co3Sn2S2, which exhibits a ferromagnetic (FM) interactions along the c-axis of the crystal and an antiferromagnetic (AFM) interactions within the ab plane. Extensive studies on the temperature dependence of the magnetism with the magnetic field along the c-axis have uncovered a number of magnetic phases. Currently, the nature and origins of the reported magnetic phases are under debate. Here we report on magnetic field orientation effects on the magnetism in Co3Sn2S2. The shape of the hysteresis loop of the Hall resistance at a fixed temperature is found to change from rectangular to bow-tie-like as the magnetic field is tilted from the c-axis towards the ab plane, resembling that reported for magnetic fields along the c-axis as the temperature approaches the Curie temperature from below. Unlike their temperature-dependent counterparts, the newly observed bow-tie-like hysteresis loops show exchange bias. Our results showcase the contribution of the in-plane AFM interactions to the magnetism in Co3Sn2S2 and demonstrate a new way to tune its magnetic phases. They also shed light on the temperature-dependent magnetic phases occurring in the magnetic field along the c-axis of the crystal.

Kagome magnet usually hosts nontrivial electronic or magnetic states drawing great interests in condensed matter physics. In this paper, we report a systematic study on transport properties of kagome magnet TmMn$_6$Sn$_6$. The prominent topological Hall effect (THE) has been observed in a wide temperature region spanning over several magnetic phases and exhibits strong temperature and field dependence. This novel phenomenon due to non-zero spin chirality indicates possible appearance of nontrival magnetic states accompanying with strong fluctuations. The planar applied field drives planar Hall effect(PHE) and anistropic magnetoresisitivity(PAMR) exhibiting sharp disconnections in angular dependent planar resistivity violating the empirical law. By using an effective field, we identify a magnetic transition separating the PAMR into two groups belonging to various magnetic states. We extended the empirical formula to scale the field and temperature dependent planar magnetoresistivity and provide the understandings for planar transport behaviors with the crossover between various magnetic states. Our results shed lights on the novel transport effects in presence of multiple nontrivial magnetic states for the kagome lattice with complicated magnetic structures.

Abstract Exploration of novel transport behavior for quantum materials is of great interest and importance for revealing exotic orders to bring new physics. In this work, we report the observation of novel prominent planar Hall effect (PHE) and anisotropic magnetoresistivity (PAMR) in strange kagomme metal KV3Sb5. The PHE and PAMR, which are driven by an in-plane magnetic field and display sharp difference from other Hall effects driven by an out-of-plane magnetic field or magnetization, exhibit exotic highfold symmetrical oscillations in sharp contrast to those following empirical rule only allowing twofold symmetrical oscillations. These highfold symmetrical oscillations exhibit strong field and temperature dependence and vanish around charge density wave (CDW) transition. The unique transport properties suggest a significant interplay of the lattice, magnetic and electronic structure in KV3Sb5. This interplay can couple the hidden anisotropy and transport electrons leading to the novel PHE and PAMR in contrast to other materials.