The structural and electronic and magnetic properties of SrFeO_n (n = 2 2.5): a GGA+U study

Using density-functional calculations within the generalized gradient approximation (GGA)+U framework, we investigate the structural, electronic, and magnetic properties of the ground states of SrFeO_n (n = 2 and 2.5). The magnetism calculations show that the ground states of both SrFeO₂ and SrFeO_2.5 have G type antiferromagnetic ordering, with indirect band gaps of 0.89 and 0.79 eV, respectively. The electronic structure calculations demonstrate that Fe cations are in the high-spin state of \left( d _z^2\right)^2\left( d _x z, d _y z\right)^2\left( d _x y\right)^1\left( d _x^2-y^2\right)^1(S=2), unlike the previous prediction of \left( d _x z, d _y z\right)^3\left( d _x y\right)^1\left( d _z^2\right)^1\left( d _x^2-y^2\right)^1(S=2) for SrFeO₂, and in the high-spin state of \left( d _x y, d _x z, d _y z, d _x^2-y^2, d _z^2\right)^5(S=5 / 2) for SrFeO_2.5.