Spin-state transitions, observed in many transition metal compounds containing Co3+ and Fe2+, may occur with the change of temperature, pressure, but also with doping, in which case the competition of single-site effects and kinetic energy of doped carriers can favor a change in the spin state. We consider this situation in a simple model, formally resembling that used for manganites in Phys. Rev. Lett. 95, 267210 (2005). Based on such a model, we predict the possibility of a jump-like change in the number of Co3+ ions undergoing spin-state transition caused by hole doping. A tendency to the electronic phase separation within a wide doping range is demonstrated. Phase diagrams with the regions of phase separation are constructed at different values of the characteristic parameters of the model.
@article{arxiv.0904.4760,
title = {Phase separation in doped systems with spin-state transitions},
author = {A. O. Sboychakov and K. I. Kugel and A. L. Rakhmanov and D. I. Khomskii},
journal= {arXiv preprint arXiv:0904.4760},
year = {2009}
}