Impact of hole doping on spin transition in perovskite-type cobalt oxides

Series of perovskite PrCo1-xNixO3-δ (x = 0-0.4) were prepared and carefully investigated to understand the spin state transition driven by hole doping and further to reveal the effect of spin state transition on electronic conduction. It is shown that with increasing doping level, the transition temperature Ts for Co(3+) ions from low-spin (LS) to intermediate-spin (IS) reduces from 211.9 K for x = 0 to 190.5 K for x = 0.4. XPS and FT-IR spectra demonstrate that hole doping promoted this transition due to a larger Jahn-Teller distortion. Moreover, a thermal activation of spin disorder caused by thermal population of the spin states for Co ions has a great impact on the electrical transport of these perovskite samples. This work may shed light on the comprehension of spin transition in cobalt oxides through hole doping, which is promising for finding new strategies of enhancing electronic conduction, especially for energy and catalysis applications.