Abstract:
We have studied the electronic and magnetic properties of the PbO-type 3d transition-metal selenides (TMSes) by first principles calculations. We find that TiSe and VSe have ionic type bonds and the other TM-Se bonds are the mixed metallic-ionic-covalent type similar to the Fe–As bonds in the ironbased superconductors. FeSe has the shortest TM-Se bond and unique stripe antiferromagnetic ground state. CrSe and MnSe have a ferromagnetic ground state, while the other TMSes have a nonmagnetic ground state. Both nonmagnetic Co dopants and magnetic Mn dopants in FeSe compress the stripe antiferromagnetic state, while the magnetic trends are different as the doping concentration increases.
......... For the spin-polarized calculations, a √ 2 × √ 2 supercell is used to find the possible magnetic ground state. The initial magnetic orderings of TM atom planes are the ferromagnetic (FM), checkerboard antiferromagnetic (AFM1) and stripe antiferromagnetic (AFM2) states [7,8,10]. The schematic illustration of AFM1 and AFM2 is given in Fig. 1(b) and (c).
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