Anomalous Hall effect in topological Weyl and nodal-line semimetal Heusler compound Co₂VAl

Abstract

Magnetic topological semimetals (TSMs) with broken time-reversal symmetry are very rare and have drawn significant attention in condensed matter physics due to their numerous intriguing topological properties. Among these various magnetic TSMs, Co$_2$-based full Heusler compounds are of current interest, since a few of these materials exhibit Weyl and nodal fermions in their topological band structure. In this work, we report a comprehensive study of anomalous Hall effect (AHE) in the ferromagnetic full Heusler compound Co$_2$VAl. Recent studies indicate that the intrinsic AHE is closely related to the Berry curvature of the occupied electronic Bloch states. The present study of Co$_2$VAl attempts to understand and explore the possibility of topology-induced AHE. The anomalous Hall resistivity $\rho^A_{xy}$ is observed to scale quadratically with the longitudinal resistivity $\rho_{xx}$. Our experimental results also reveal that the anomalous Hall conductivity (AHC) is $\sim 85\, S/cm$ at 2 K with an intrinsic contribution of $\sim 75.6\, S/cm$, and is nearly insensitive to temperature. The first principle calculations note that the Berry curvature originated from a gapped nodal line and symmetry-protected Weyl nodes near the Fermi level ($E_F$) is the main source of AHE in this compound. Thus, this investigation on Co$_2$VAl discloses that it is a ferromagnetic Weyl and nodal-line topological semimetal. The theoretically calculated AHC is in well agreement with the experimentally obtained AHC.

Intrinsically dominated anomalous Hall effect in pulsed laser deposited epitaxial Co2MnGe ferromagnetic full Heusler alloy thin films

“…Double magnon scattering contributes to the T 9/2 -dependence at low temperatures (region-I) and T 7/2 -dependence at higher temperatures (region-II). 43 Therefore, half-metallic nature of the Co 2 MnGe epitaxial film is evidenced from the resistivity-temperature data in the entire range of 2–300 K.…”

Hydrostatic pressure-induced anomalous hall effect in Co2FeSi semimetal

“…The first one is zero-dimensional (0D) nodal points, which include Weyl points [1], Dirac points [5], triple points [6] and other higher degenerate nodal points [7]. The One-dimensional (1D) nodal-line (NL) systems [8] such as nodal rings [9], nodal chains [10], and nodal nets [10] are of second type. Two-dimensional (2D) nodal surfaces [11] are the third one.…”

“…The family of Heusler compounds is considerably large comprising more than 1000 members and can display paramagnetic, ferromagnetic and antiferromagnetic properties and fascinating anomalous electric, thermal and thermoelectric transport properties [37]. The AHC has been reported to be intrinsic in several Heusler compounds such as Co 2 CrGa, Co 2 VAl,Co 2 FeGe,Co 2 MnGa [8,29,36,38,39]. The major challenge in these compounds is to design Heusler compounds with large anomalous transport properties and their tunability of intrinsic anomalous behavior i.e.…”