Electronic structure of RMn2Si2 (R = Y, La) intermetallics: DFT and XPS studies

The first-principles density functional theory (DFT) calculations of layered RMn2Si2 (R = Y, La) intermetallic compounds with Mn-adjacent layers separated by two Si non-magnetic layers and between them – R-layer (the ThCr2Si2-type structure), are presented. The analysis of the partial and total densities of states (DOS) of both compounds (YMn2Si2 and LaMn2Si2) demonstrates their metallic and magnetic character as well. The noncollinear magnetic ordering with canted moments is found in LaMn2Si2 with moments of 2.99 μB and 0.02 μB for the Mn and the La ions, respectively. In YMn2Si2 the Mn moments form the collinear antiferromagnetic order, and the Y ions are nonmagnetic. Calculated charge density distribution within the cell of RMn2Si2 indicates a covalent bonding between the Mn- and Si-layers of the compound and ionic type of bonding for R ions. It is found that hybridization of the Mn 3d-states with Si 3p-states induces a slight magnetization of Si ions for both compounds. In LaMn2Si2, as compared with YMn2Si2, the MnSi and Mn-R hybridization is weakened as a result of crystal lattice expansion, orbital momentum appearance and spin-orbit interaction influence. Therefore, the Mn d3z2-r2 and dx2-y2 states can participate in the MnMn intra- and interplane interactions, which is likely the reason of formation of the canted magnetic structure. The results of DFT calculations are in agreement with specially performed XPS measurements of YMn2Si2 and LaMn2Si2.