Magnetic Properties and Scaling Behavior in Perovskite-like La 0.7 (Ba 1−x Pb x ) 0.3 CoO 3 System

In this study, we used x-ray diffraction patterns and dc magnetic measurements to investigate the crystallographic structure, magnetic properties and scaling behavior of the distorted perovskite La 0.7 (Ba 1−x Pb x ) 0.3 CoO 3 (0 ≤ x ≤ 0.5) system with a constant ratio of Co 4+ /Co 3+ . Samples with x = 0.0 and 0.1 were crystallized in the cubic structure with a ∼ 7.76 Å whereas samples with x ≥ 0.2 were crystallized in an orthorhombic Pbnm space group with a ∼ b ∼ 5.50 Å and c ∼ 7.85 Å. For all our samples the spin-glass-like behavior were observed in low temperature and low field ranges. The Pb 2+ substitution on Ba 2+ site does not significantly affect the ferromagnetic transition temperature T C , but does introduce large variation in the magnetic strength. In both the ferromagnetic and paramagnetic states the minimum values of the average effective moments provided by every Co ion occur at x = 0.3. We also observed the scaling behaviors of magnetic data in all samples. The derived values of the critical exponents (β, γ, δ) were consistent with those predicted by mean field theory and a three-dimensional Heisenberg model.