Evidence for a temperature-induced spin-state transition of Co3+ in La2-xSrxCoO4

TL;DR

This study investigates a temperature-induced spin-state transition of Co3+ in La2-xSrxCoO4, revealing a transition from low-spin to higher spin states at elevated temperatures through magnetic susceptibility analysis.

Contribution

It provides experimental evidence and theoretical analysis of the spin-state transition of Co3+ in La2-xSrxCoO4 at high temperatures.

Findings

Susceptibility increases above room temperature indicating a spin-state transition.

Co3+ transitions from low-spin to high- or intermediate-spin states with temperature.

Full-multiplet calculations support the thermal population of higher spin states.

Abstract

We study the magnetic susceptibility of mixed-valent La2-xSrxCoO4 single crystals in the doping range of 0.5<= x <= 0.8 for temperatures up to 1000 K. The magnetism below room temperature is described by paramagnetic Co2+ in the high-spin state and by Co3+ in the non-magnetic low-spin state. Above room temperature, an increase in susceptibility compared to the behavior expected from Co2+ is seen, which we attribute to a spin-state transition of Co3+. The susceptibility is analyzed by comparison to full-multiplet calculations for the thermal population of the high- and intermediate-spin states of Co3+.