Electronic and magnetic structures of bilayer La3Ni2O6and trilayer La4Ni3O8nickelates from first principles

We revisit the electronic and magnetic structure of bilayer, La${}_{3}$Ni${}_{2}$O${}_{6}$ and trilayer, La${}_{4}$Ni${}_{3}$O${}_{8}$ nickelates, in terms of detailed first-principles calculations. Through construction of an axial orbital, we show that the crystal-field splitting obtained in a single layer case, is modified substantially in the multilayer case leading to a near degeneracy of several levels and a possible bistability between low spin and high spin state of Ni in specific cases. The issue needs to be settled by further experimental studies, followed by theoretical investigations.