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Space Group and Fundamental Vibrations of the (RElBa2Cu3O7)m (RE2Ba2Cu3O7)n Superlattices

Published online by Cambridge University Press:  26 February 2011

V. Yu. Mirovitskii
V. Yu. Mirovitskii*
Affiliation:
Instituto for Power Engineering, Academy of Sciences of Moldova, Grosul Str.5. Kishinev 277038. Moldova, USSR
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Abstract

The (RE1Ba2Cu3O7)m (RE2Ba2Cu3O7)n superlattices (SL) with the superporiod d along [100]. [010] and [001] have been considered as a single crystals with primitive cells formally multiplied duo to ordering of rare earth atoms in an initial hypothetical mixed system (RE1pRE21-p)Ba2Cu3O7 By means of symmetry methods it is found that the suporporiodicity in those SL, unlike Ge/Si or GaAs/AlAs. keeps the initial space group Pmmm at any m and n. On the contrary, the obtained Table of the SL atoms distribution over Wyckoff positions indicates that the type, multiplicity and the number of the positions essentially depend on d and Cm.nD. Those data are used for group thoorotical classification of the fundamental vibrations of SL's. The analysis of spectrum changes under transformation from the initial compound to SL is performed. In particular, it is found out that already at the lowest m and n the oven vibrations of RE, Cul and Ol, occupying only one-fold positions in the initial structure, occur. Also for each d the typo of spectrum is shown to depend on both m+n and the fact if the pair (m.n) is even-oven, odd-odd or oven-odd.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 275: Symposium S – Layered Superconductors: Fabrication, Properties and Applications , 1992 , 221
Copyright
Copyright © Materials Research Society 1992

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References

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