Local A-Site Layering in Rare-Earth Orthochromite Perovskites by Solution Synthesis

Cation size effects were examined in the mixed A-site perovskites La_0.5 Sm_0.5 CrO₃ and La_0.5 Tb_0.5 CrO₃ prepared through both hydrothermal and solid-state methods. Atomically resolved electron energy loss spectroscopy (EELS) in the transmission electron microscope shows that while the La and Sm cations are randomly distributed, increased cation-radius variance in La_0.5 Tb_0.5 CrO₃ results in regions of localised La and Tb layers, an atomic arrangement exclusive to the hydrothermally prepared material. Solid-state preparation gives lower homogeneity resulting in separate nanoscale regions rich in La³⁺ and Tb³⁺ . The A-site layering in hydrothermal La_0.5 Tb_0.5 CrO₃ is randomised upon annealing at high temperature, resulting in magnetic behaviour that is dependent on synthesis route.