Magnetic properties of Monoclinic Fe3Se4 doped with transition metals

We report density functional theory (DFT) study of the magnetic properties of Fe3Se4 doped with transition metals, TM (Co, Cr, Ni and Mn), where TM ions are doped in Fe sites to yield Fe
3−x
(TM)
x
Se
4
(x = 0.5). Screening of the exchange coupling interaction and magnetization modifications were performed upon the substitution of Fe by 3d-transition metals at various Fe sites in the Fe
3
Se
4
structure. Our study reveals that doping of Fe
3
Se
4
with 3d-elements at Fe sites does not remove antiferromagnetic (AFM) coupling across layers. Although a slight increase in magnetization can be obtained at low Ni-doping. The origin of this increase could be attributed to the AFM superexchange coupling of Fe across the Se planes. This coupling is exhibited by elements with more than half-filled electron shell, i.e. Fe is such an element. Moreover, the exchange coupling between layers of Fe increases strongly as function of interlayer spacing (a lattice parameter) for both pristine and TM-doped Fe
3
Se
4
, while the magnetizations of Fe
3
Se
4
alloys do not change significantly.