Semiconducting spin glass to metallic ferromagnetic state phase transition in double-substituted La1-xSrxCo1-yNiyO3-γ perovskites

A comprehensive study of the structural, magnetic, and transport properties of double-substituted La1-xSrxCo1-yNiyO3-gamma (0.1 x 0.5, 0.05 y 0.25) perovskite systems was carried out. The average oxidation number of Co ions was found to be 3+ for the most subsystems. The existence of several characteristic concentration regions for various degrees of substitution in the A (La, Sr) and B (Co, Ni) sublattices is shown. Low levels of Sr and Ni ion substitution subsystems demonstrate cluster spin-glass behavior with a semiconducting character of the conductivity and a diamagnetic low-spin (LS) Co3+ matrix. An increase of Ni substitution leads to the stabilization of intermediate-spin (IS) Co3+ ions in CoO6 octahedra, approaching the percolation threshold of ferromagnetic clusters. For strongly Sr-substituted subsystems an effect of stabilization of IS Co3+ is not observed, since the contribution of this effect is smaller than the effect of the dilution by antiferromagnetically interacting Ni ions. In this case, an increase of Ni content leads to a decrease in the magnetic ordering temperature Tmo and magnetization values. For weakly Sr-substituted systems, on the contrary, it leads to their growth. Anomalies in the conductivity dependences for several subsystems are due to the thermally induced spin crossover of the part of Co3+ ions, first from the LS to the IS state, and then to the mixed IS/high-spin (HS) state, similar to the parent LaCoO3.

Automated summary

A comprehensive study was conducted on the structural, magnetic, and transport properties of double-substituted La1-xSrxCo1-yNiyO3-gamma perovskite systems. Various characteristic concentration regions were observed in the A and B sublattices. Interestingly, low levels of Sr and Ni substitution exhibited cluster spin-glass behavior with semiconducting conductivity and diamagnetic low-spin (LS) Co3+ matrix. The stabilization of intermediate-spin (IS) Co3+ ions in CoO6 octahedra and its effect on ferromagnetic clusters were influenced by Ni substitution. Additionally, the effect of stabilization of IS Co3+ was not observed in strongly Sr-substituted systems due to the dilution effect of antiferromagnetic Ni ions. The study also revealed anomalies in the conductivity dependences attributed to the thermal-induced spin crossover of Co3+ ions.