Effect of transition metals doping in magnetic properties of Fe₃Se₄

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_2.5(TM)_0.5Se₄. Screening of the exchange coupling interaction and magnetization modifications were performed upon the substitution of Fe by transition metals at various Fe sites in the Fe₃Se₄ structure. Our study reveals that doping of Fe₃Se₄ with TM elements at Fe sites does not remove antiferromagnetic (AFM) coupling across layers, thus, not increasing the magnetization. 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 (c lattice parameter) for both pristine and TM-doped Fe₃Se₄, while the magnetizations of Fe₃Se₄ alloys do not change significantly.