Electronic and Magnetic Structures of Hole Doped Trilayer La_4–<i>x</i>Sr_<i>x</i>Ni₃O₈from First-Principles Calculations

Abstract

The magnetic and electronic properties of trilayer La₄Ni₃O₈, similar to hole-doped cuprates, are investigated by performing full-potential linearized augmented plane wave method-based spin-polarized calculations with LDA and GGA functionals including Hubbard U parameters to account for strong correlation effects. On the basis of these calculations, we found that La₄Ni₃O₈ is a C-type anti-ferromagnetic (C-AFM) Mott insulator in agreement with previous experimental and theoretical observations. Our calculations suggest that the two crystallographically nonequivalent nickel atoms Ni1 and Ni2 are found to be in high-spin state with an average valency of +1.33. Intermediate band-gap states are originated from d_z² electrons of both types of Ni ions after including the strong correlation effects. To understand the role of hole doping on electronic structure, phase stability, and magnetic properties of La₄Ni₃O₈, similar calculations were performed for La_4-xSr_xNi₃O₈ as a function of x, using the supercell approach. We found that the hole doping brings insulator-to-metal transition without changing the C-AFM ordering, though the magnetic moment is enhanced at both Ni sites. Moreover, these Ni atoms are always in an average valence state irrespective of hole doping or volume change. So the electronic properties of hole-doped La₄Ni₃O₈ cannot be compared with hole-doped cuprates that are high-T_C superconductors.