Landau–Ginzburg free energy study of spin state phase transition in LaCoO3

LaCoO3 (LCO) undergoes a cubic to rhombohedral structural phase transition at ∼1600 K, a metal–insulator transition at ∼550 K, and a spin-state transition at ∼100 K. The thermodynamics of spin-state phase transitions for LCO have been studied using the 2-4-6 Landau–Ginzburg (LG) free energy functional (ΔG) developed in terms of mode amplitude of octahedral tilt (primary order parameter), symmetry-adapted strains, and pure electronic free energy (depicting gradual change of high-spin population f