Electronic and magnetic structures of bilayer La3Ni2O6 and trilayer La4Ni3O8 nickelates from first principles

We revisit the electronic and magnetic structure of bilayer, La3Ni2O6 and trilayer, La4Ni3O8 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.