Disorder-induced topological properties in CoFeCrZ (Z = Al and Ga) Heusler alloys: From spin gapless semiconductor to magnetic Weyl semimetal

Abstract

The effect of structural disorder on the electronic, magnetic, and topological properties of quaternary Heusler alloys CoFeCrZ (Z = Al and Ga) has been investigated in detail both theoretically and experimentally. In the ideal Y structure, these alloys exhibit spin gapless semiconducting behaviour. However, the introduction of B2-type disorder destabilizes this phase and drives the system into a magnetic Weyl semimetallic state. The disorder generates Weyl nodal points for both up and down spin channels, leading to a pronounced enhancement of the intrinsic anomalous Hall conductivity. We attribute this enhancement to an increase in Berry curvature. Furthermore, topologically protected surface states with Fermi arcs emerge in the disordered phase. Our results establish disorder as a crucial parameter to tune for realizing topological semimetallic behaviour in CoFeCrZ (Z = Al and Ga) Heusler alloys.