Effects of magnetic dopants in (Li_{0.8}M_{0.2}OH)FeSe (M = Fe, Mn, Co): a density-functional theory study using band unfolding technique

The effects of Fe dopants in (Li$_{0.8}$Fe$_{0.2}$OH)FeSe on the electronic band structure are investigated by band unfolding ($k$-projection) technique based on first-principles supercell calculations. Doping 20\% Fe into the LiOH layers has significant effects on the band structure, that is, the Fe impurities doping electrons to the FeSe layers not only shift the Fermi level, but also induce substantial changes in the profile of bands around the Fermi level. However, the magnetic ordering in the dopants has minor effects on the band structure due to the fact that there is only a weak bonding between the LiOH and FeSe layers. Electronic bands for the surface FeSe layer show noticeable differences from those for inner layers in both the location of the Fermi level and details of the bands near the high symmetry points. The band structure for the surface FeSe layer where the Fe atoms are in checkerboard antiferromagnetic order is consistent with angle-resolved photoemission spectroscopy results. Mn and Co have similar doping effects on the band structure of (LiOH)FeSe.