Magnetic properties of LixCoO2 for x=0.94,0.75,0.66 and 0.51 were investigated in frames of method combining Generalized Gradient Approximation with Dynamical Mean--Field Theory (GGA+DMFT). We found that a delicate interplay between Hund's exchange energy and t2g−eg crystal field splitting is responsible for the high spin to low spin state transition for Co4+ ions. The GGA+DMFT calculations show that at small doping level the Co4+ ions adopt high spin state, while delithiation results in increase of the crystal field splitting and low spin state becomes preferable. The Co3+ ions were found to stays in the low spin configuration for any x.
@article{arxiv.1608.01475,
title = {Doping induced spin state transition in Li$_x$CoO$_2$ as studied by the GGA+DMFT calculations},
author = {A. O. Shorikov and V. V. Gapontsev and S. V. Streltsov and V. I. Anisimov},
journal= {arXiv preprint arXiv:1608.01475},
year = {2018}
}