Topological Spin Semimetal Feature in a Fully Compensated Ferrimagnet CoRuVSi

Abstract

We have identified the quaternary Heusler alloy, CoRuVSi, as a new member of the recently discovered spin semimetals class through experimental and theoretical studies. At room temperature, CoRuVSi crystallizes in a cubic structure with partial L2 1 -type disorder according to synchrotron X-ray diffraction analysis. Magnetization data suggest a small net moment of ∼0.13 μ B (f.u.) −1 , attributed to the disorder, with no clear magnetic ordering at low temperatures. Electrical resistivity measurements provide compelling evidence of semimetallicity dominated by two-carrier conduction, while magnetoresistance data reveal a positive, sublinear, and nonsaturating behavior. Point-contact Andreev reflection spectra show a spin polarization of ∼50%, in good agreement with the simulated results. Furthermore, CoRuVSi exhibits a high thermopower factor of 0.7 mW m −1 K −2 at room temperature. Our ab initio simulations not only confirm the unique semimetallic nature of the material but also reveal a linear band crossing at ∼0.4 eV below the Fermi level due to band inversion, as well as topological nontrivial features of the band structure corroborated with the simulated Berry curvature, intrinsic anomalous Hall conductivity, and the Fermi surface. We have used a special quasi-random structure to simulate the partial L2 1 disorder, which plays a key role in correctly explaining the magnetism and anomalous Hall effect. The simulated anomalous Hall conductivity values for the fully and partially ordered structures are found to be 102 and 52 S (cm) −1 , respectively, with the latter in fairly good agreement with the experimentally measured value of 45 S (cm) −1 . The coexistence of these intriguing properties within a single material offers valuable insights for identifying other potential materials belonging to the same class using a similar strategy.