Nontrivial Topological Features and Griffith’s-Phase Behavior in CrFeVGa Probed by Experiment and Theory

Abstract

We report a combined theoretical and experimental study of the topological semimetal CrFeVGa with an emphasis on the role of atomic disorder on the magnetoelectronic properties. CrFeVGa belongs to the quaternary Heusler alloy family and crystallizes in the cubic structure with B2 disorder. It is found that the disorder plays a crucial role in quenching the magnetization (net moment $\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\phantom{\rule{0.2em}{0ex}}{\ensuremath{\mu}}_{B}$ per formula unit) and other anomalies. Ac and dc magnetization data reveal the occurrence of Griffith's-phase-like behavior in the presence of small magnetic clusters with a weak antiferromagnetic or ferrimagnetic ordering. A nonsaturating, linear positive magnetoresistance is observed even at 70 kOe, in a wide temperature range, which is attributed to the quantum linear magnetoresistance arising due to the zero- or small-gap band structure. Hall measurements show some anomalous behavior (including an anomalous Hall conductivity ${\ensuremath{\sigma}}_{xy0}=270\phantom{\rule{0.2em}{0ex}}\mathrm{S}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ and an anomalous Hall angle of 0.07 at 2 K) with a significant contribution from the semimetallic bands. Hall data analysis also reveals the presence of some non-negligible topological Hall contribution, which is significant at low temperatures. Ab initio calculations confirm the topological Weyl behavior of CrFeVGa, which originates from a unique combination of broken time-reversal symmetry and noncentrosymmetry. The nontrivial band topology stems from the $p$ and $d$ states of vanadium, which overlap near the Fermi level. The presence of multi-Weyl points (24 pairs) near the Fermi level causes a large Berry curvature and hence reasonably high anomalous Hall conductivity. The coexistence of so many emerging features in a single material is rather rare and thus opens up new avenues for future topological and spintronics-based research.