The ferrimagnetic super-exchange interactions in post-annealed Bi4Ti3O12-La0.5Sr0.5MnO3

Bi₄Ti₃O₁₂-La_0.5Sr_0.5MnO₃ (BIT-LSMO) is a promising naturally superlattice-structured compound due to its ferroelectric semiconducting nature besides other abundant tunable physical properties. Among those, we find its magnetism varies with the valence of Mn in samples treated under different post-annealing conditions. The ferrimagnetic Curie temperatures (T_c) are determined to be around 43 K for the hydrothermal sample and the pulverized powders of ceramic processed under vacuum at 700 ℃, 800 ℃, while two T_cs around 43 K and 76 K are found for that processed under vacuum at 900 ℃. According to the small saturation magnetic moment revealed by the M−H curve, we conclude that the 43 K T_c originates from the antiferromagnetically coupled exchange of Mn⁴⁺–O^2-–Mn³⁺, while the 76 K T_c originates from the antiferromagnetically coupled exchange of Mn³⁺–O^2-–Mn²⁺. This provides a feasible route to manipulate the magnetism in bismuth layer-structured oxides.