Monoclinic structure of La1-xSrxMnzO₃ (x=0.212,z=0.958)

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Tamazyan, Rafael ; van Smaalen, Sander ; Arsenov, A. ; Mukovskii, Yakov:
Monoclinic structure of La1-xSrxMnzO₃ (x=0.212,z=0.958).
In: Physical Review B. Bd. 66 (2002) Heft 22 . - No. 224111.
ISSN 0163-1829
DOI: https://doi.org/10.1103/PhysRevB.66.224111

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Abstract

Single-crystal x-ray diffraction is used to show that the crystal structure of La0.788Sr0.212Mn0.958O3 is monoclinic at room temperature. The Curie temperature of this sample is 324 K. The space group is determined as I2/c with lattice parameters a=5.4863 (3) Å, b=5.5361 (3) Å, c=7.7941 (4) Å, and β=90.74 (2)°. The crystals are found to be multiply twinned with nonequal volume fractions of the twin domains. A structure refinement against the diffraction data of a twinned crystal converged at R=0.040. The structure model involves the same pattern of tiltings of the MnO6 octahedra as was found in the rhombohedral structure. The principal distortions of the monoclinic structure as compared to the rhombohedral structure are deviations of the O-Mn-O bond angles within the MnO6 octahedra from 90°. It is argued that the small size of the monoclinic splitting and the very weak additional reflections might not have been visible in neutron diffraction. Our finding of monoclinic symmetry for this compound calls for a revision of the phase diagram of La1−xSrxMnO3 compounds (0<x<1).