Evolution of magnetic oxygen states in Sr-doped LaCoO$_3$

TL;DR

This study explores how Sr doping influences magnetic oxygen states in LaCoO3, revealing the formation and growth of magnetic O-hole states and their relation to ferromagnetic clusters through spectroscopy and first-principles calculations.

Contribution

It provides new insights into the evolution of magnetic oxygen states in Sr-doped LaCoO3 using combined experimental and theoretical approaches.

Findings

Sr doping induces magnetic O-hole states above E_F.

Magnetic clusters form within a nonmagnetic matrix at low doping.

Doping introduces holes at the Fermi level with significant O 2p and Co t2g character.

Abstract

Magnetism in La$_{1-x}$Sr$_x$CoO$_3$ as a function of doping is investigated with X-ray absorption spectroscopy and X-ray magnetic circular dichroism at the O K edge, and corresponding first principles electronic structure calculations. For small x, the spectra are consistent with the formation of ferromagnetic clusters occurring within a nonmagnetic insulating matrix. Sr-induced, magnetic O-hole states form just above E$_F$ and grow with increasing Sr doping. Density functional calculations for x = 0 yield a nonmagnetic ground state with the observed rhombohedral distortion and indicates that doping introduces holes at the Fermi level in magnetic states with significant O 2p and Co t$_{2g}$ character for the undistorted pseudocubic structure. Supercell calculations show stronger magnetism on oxygen atoms having more Sr neighbors.