First-principles study of electronic and magnetic properties of Fe1−xTMxSe0.5Te0.5 alloys (TM ≡ Cr, Mn, Co, Ni)

We have studied the effects of transition metal (TM) substitution on Fe sub-lattice in Fe1−xTMxSe0.5Te0.5 (TM ≡ Cr, Mn, Co, Ni and x = 0, 0.01, 0.05, 0.10) in terms of changes in its electronic and magnetic properties. The calculations were performed with the Korringa-Kohn-Rostoker (KKR) Atomic Sphere Approximation (ASA) method within the coherent-potential approximation (CPA). Our spin-polarized calculations show these alloys to be magnetic in nature. We discuss the calculated density of states (DOS), band structures and Fermi surfaces (FS) in terms of the contributions of Fe3d64s2, Cr3d54s1, Mn3d54s2, Co3d74s2, Ni3d84s2 and Se4s24p4 outer most electrons. Our results indicate that the effects of doping on the electronic properties are significant with respect to parent FeSe and FeSe0.5Te0.5 superconductor. We have also estimated the value of electron-phonon mass enhancement factor λ (which is the sum of electron-phonon coupling constant and the electron-electron interaction present in the material) to calculate the superconducting transition temperature Tc for the TM-doped FeSe0.5Te0.5. Hopfield parameters are also calculated from the charge self-consistent potentials obtained from KKR-ASA CPA method.