Mn and Co Charge and Spin Evolutions in LaMn1-xCoxO3 Nanoparticles

Abstract

The charge and spin-state evolution of manganese and cobalt in the LaMn1-xCoxO3 (x = 0.00, 0.25, 0.50, 0.75, and 1.00) perovskite nanoparticles have been studied with soft X-ray absorption spectroscopy. The results show a gradual increase in the average oxidation state of both Mn and Co ions with cobalt doping. The average valence of the LaMn1-xCoxO3 samples remains close to 3.0, with the Mn valence increasing from 3.1 to 4.0 and the Co valence increasing from 2.0 to 3.0. The symmetry of Mn and Co was determined using multiplet calculations. Calculating the intensity-area of the oxygen K pre-edge feature confirmed an increase in covalency with increasing Mn and Co oxidation state. The ground-state composition of Mn3+ in LaMnO3, and Co3+ in LaCoO3, was investigated, and it was found that Mn3+ (D4h) and Co3+ (Oh) are mainly in their low-spin state, with 10-20% admixture of high-spin state contributions into a mixed spin ground state.