  We report a theoretical investigation of effects of Mn and Co substitution in
the transition metal sites of the kagome-lattice ferromagnet, Fe3Sn2. Herein,
hole- and electron-doping effects of Fe3Sn2 have been studied by
density-functional theory calculations on the parent phase and on the
substituted structural models of Fe3-xMxSn2 (M = Mn, Co; x = 0.5, 1.0). All
optimized structures favor the ferromagnetic ground state. Analysis of the
electronic density of states (DOS) and band structure plots reveals that the
hole (electron) doping leads to a progressive decrease (increase) in the
magnetic moment per Fe atom and per unit cell overall. The high DOS is retained
nearby the Fermi level in the case of both Mn and Co substitutions. The
electron doping with Co results in the loss of nodal band degeneracies, while
in the case of hole doping with Mn emergent nodal band degeneracies and
flatbands initially are suppressed in Fe2.5Mn0.5Sn2 but re-emerge in Fe2MnSn2.
These results provide key insights into potential modifications of intriguing
coupling between electronic and spin degrees of freedom observed in Fe3Sn2.
