Phase separation in doped systems with spin-state transitions

TL;DR

This paper models how doping influences spin-state transitions in transition metal compounds, predicting abrupt changes and phase separation phenomena, with implications for understanding complex magnetic and electronic behaviors.

Contribution

It introduces a simple model to predict doping-induced spin-state changes and demonstrates the tendency for electronic phase separation in doped systems.

Findings

Prediction of jump-like changes in Co$^{3+}$ spin states due to doping

Demonstration of phase separation over a wide doping range

Construction of phase diagrams showing regions of phase separation

Abstract

Spin-state transitions, observed in many transition metal compounds containing Co$^{3+}$ and Fe$^{2+}$, 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 Co$^{3+}$ 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.