Magnetic Topological Alloys Based on the Cd3As2 Dirac Semimetal: Doping with Cr, Mn, and Fe

According to theoretical models, the doping of a Dirac semimetal with magnetic atoms splits the Dirac cone into two Weyl cones, thus forming a magnetic Weyl semimetal attractive for applications. In this work, such phenomenon is investigated ab initio on an example of the Cd 3 As 2 Dirac semimetal doped with Cr, Mn, and Fe. For the cases of ferromagnetic and antiferromagnetic ordering in (Cd 1‒ x M x ) 3 As 2 alloys (M = Cr, Mn, Fe), the band structure, Fermi surface, electron velocity at the Fermi level, and the Drude plasma frequency are calculated, and the relaxation time in the limit T → 0 K is estimated. The calculations demonstrate that one Weyl cone in ferromagnetic alloys is usually destroyed due to the hybridization of electronic states of Cd 3 As 2 with M 3 d orbitals. The condition for the conservation of the second Weyl cone is its falling into an energy window free of M 3 d states. The existence of such windows is closely related to the energy and filling of 3 d $$ \uparrow $$ and 3 d ↓ bands of M atoms, the type of spin ordering (ferro- or antiferromagnetic), and the chemical composition of the alloy. In particular, such windows are absent in antiferromagnetic alloys, except the case of M = Mn. The estimates show that the Weyl cone, if preserved, dominates in the transport properties of (Cd 1‒ x M x ) 3 As 2 , which agrees with the available experimental results.