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Register a new userMagnetization governed magnetoresistance anisotropy in topological semimetal CeBi
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Magnetic topological semimetals, the latest member of topological quantum materials, are attracting extensive attention as they may lead to topologically-driven spintronics. Currently, magnetotransport investigations on these materials are focused on anomalous Hall effect. Here, we report on the magnetoresistance anisotropy of topological semimetal CeBi, which has tunable magnetic structures arising from localized Ce 4f electrons and exhibits both negative and positive magnetoresistances, depending on the temperature. We found that the angle dependence of the negative magnetoresistance, regardless of its large variation with the magnitude of the magnetic field and with temperature, is solely dictated by the field-induced magnetization that is orientated along a primary crystalline axis and flops under the influence of a rotating magnetic field. The results reveal the strong interaction between conduction electrons and magnetization in CeBi. They also indicate that magnetoresistance anisotropy can be used to uncover the magnetic behavior and the correlation between transport phenomena and magnetism in magnetic topological semimetals.
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Topological materials often exhibit remarkably linear, non-saturating magnetoresistance (LMR), which is both of scientific and technological importance. However, the role of topologically non-trivial states in the emergence of such a behaviour has been difficult to establish in experiments. Here, we show how strong interaction between the topological surface states (TSS) with a positive g-factor and the bulk carriers can lead to a smearing of the Landau levels giving rise to an LMR behavior in a semi-metallic Heusler compound. The role of TSS is established by controllably reducing the surface-bulk coupling by a combination of substitution alloying and the application of high magnetic field, when the LMR behavior transmutes into a quantum Hall phase arising from the TSS. Our work establishes that small changes in the coupling strength between the surface and the bulk carriers can have a profound impact on the magnetotransport behavior in topological materials. In the process, we lay out a strategy to both reveal and manipulate the exotic properties of TSS in compounds with a semi-metallic bulk band structure, as is the case in multi-functional Heusler compounds.
Multiple mechanisms for extremely large magnetoresistance (XMR) found in many topologically nontrivial/trivial semimetals have been theoretically proposed, but experimentally it is unclear which mechanism is responsible in a particular sample. In this article, by the combination of band structure calculations, numerical simulations of magnetoresistance (MR), Hall resistivity and de Haas-van Alphen (dHvA) oscillation measurements, we studied the MR anisotropy of SiP$_{2}$ which is verified to be a topologically trivial, incomplete compensation semimetal. It was found that as magnetic field, $H$, is applied along the $a$ axis, the MR exhibits an unsaturated nearly linear $H$ dependence, which was argued to arise from incomplete carriers compensation. For the $H$ $parallel$ [101] orientation, an unsaturated nearly quadratic $H$ dependence of MR up to 5.88 $times$ 10$^{4}$$%$ (at 1.8 K, 31.2 T) and field-induced up-turn behavior in resistivity were observed, which was suggested due to the existence of hole open orbits extending along the $k_{x}$ direction. Good agreement of the experimental results with the simulations based on the calculated Fermi surface (FS) indicates that the topology of FS plays an important role in its MR.
We report the observation of colossal positive magnetoresistance (MR) in single crystalline, high mobility TaAs2 semimetal. The excellent fit of MR by a single quadratic function of the magnetic field B over a wide temperature range (T = 2-300 K) suggests the semiclassical nature of the MR. The measurements of Hall effect and Shubnikov-de Haas oscillations, as well as band structure calculations suggest that the giant MR originates from the nearly perfectly compensated electrons and holes in TaAs2. The quadratic MR can even exceed 1,200,000% at B = 9 T and T = 2 K, which is one of the largest values among those of all known semi-metallic compounds including the very recently discovered WTe2 and NbSb2. The giant positive magnetoresistance in TaAs2, which not only has a fundamentally different origin from the negative colossal MR observed in magnetic systems, but also provides a nice complemental system that will be beneficial for applications in magnetoelectronic devices
The topological semimetal $beta$-Ag2Se features a Kramers Weyl node at the origin in momentum space and a quadruplet of spinless Weyl nodes, which are annihilated by spin-orbit coupling. We show that single crystalline $beta$-Ag2Se manifests giant Shubnikov-de Haas oscillations in the longitudinal magnetoresistance which stem from a small electron pocket that can be driven beyond the quantum limit by a field less than 9 T. This small electron pocket is a remainder of the spin-orbit annihilatedWeyl nodes and thus encloses a Berry-phase structure. Moreover, we observed a negative longitudinal magnetoresistance when the magnetic field is beyond the quantum limit. Our experimental findings are complemented by thorough theoretical band structure analyses of this Kramers Weyl semimetal candidate, including first-principle calculations and an effective k*p model.
We report the synthesis and properties of two new insulating phases of SrFeO3-d with introduction of oxygen deficiencies in metallic SrFeO3 ; one with 0.15 < d < 0.19 (sample A)and the other above d = 0.19 (sample B). Sample A shows large negative magnetoresistance around the charged ordering (CO) temperature with magnetic anomalies seen in the temperature dependent resistivity,magnetization and M-H hysteresis loops. Sample B shows a smooth insulating behavior with no thermal hysteresis in the resistivity and with a small positive magnetoresistance. cac and cdc show multiple features associated with a frustrated magnetic order (helical) due to competing ferro- and antiferromagnetic interactions. The competing effects of ferro- and antiferromagnetic phases extend up to T ~ 230 K revealing a new high temperature scale in this system. These observations are discussed in the context of magnetic interactions associated with the varying Fe4+/Fe3+ ratio.
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