High pressure effects on the Jahn-Teller distortion in perovskite La_(0.5-x)Bi_xCa_(0.5)MnO_3

摘要

X-ray diffraction studies were carried out on the distorted perovskite La_(0.5-x)Bi_xCa_(0.5)MnO_3 (x=0,0.5,0.1,0.15,0.2,0.25) under high pressure at room temperature y the energy-dispersive technique. The unusual expansion of the 202-040 d-spacing under pressure was observed and accompanied by a remarkable decrease of the Jahn-Teller distortion in MnO_6 octahedra. The change of the Mn-O bond angle brings about the disappearance of the basal-plane distortion mode Q_2. The substitution of Bi~(3+) for La~(3+) in the system introduces more distortions, which is ascribed to the unique lone pair characteristics of bismuth.