Interplay Of Electron Correlations, Spin-Orbit Couplings, And Structural Effects For Cu Centers In The Quasi-Two-Dimensional Magnet Incu2/3v1/3o3

Less common ligand coordination of transition-metal centers is often associated with peculiar valence-shell electron configurations and outstanding physical properties. One example is the Fe+ ion with linear coordination, actively investigated in the research area of single-molecule magnetism. Here we address the nature of 3d(9) states for Cu2+ ions sitting in the center of trigonal bipyramidal ligand cages in the quasi-two-dimensional honeycomb compound InCu2/3V1/3O3 , whose unusual magnetic properties were intensively studied in the recent past. In particular, we discuss the interplay of structural effects, electron correlations, and spin-orbit couplings in this material. A relevant computational finding is a different sequence of the Cu (xz, yz) and (xy, x(2) -y(2)) levels compared to existing electronic-structure models, which has implications for the interpretation of various excitation spectra. Spin-orbit interactions, both first- and second-order, turn out to be stronger than previously assumed, suggesting that rather rich single-ion magnetic properties can in principle be achieved also for the 3d(9) configuration by properly adjusting the sequence of crystal-field states for such less usual ligand coordination.