DYNAMICS OF THE CU-O CHAIN IN YBA2CU3O7-DELTA - EMISSION MOSSBAUER STUDIES

被引：11

作者：

HOMONNAY, Z

NATH, A

机构：

[1] Department of Chemistry, Drexel University, Philadelphia, 19104, Pennsylvania

来源：

JOURNAL OF SUPERCONDUCTIVITY | 1990年 / 3卷 / 04期

关键词：

SUPERCONDUCTIVITY; CU-O CHAIN; DYNAMICS; MOSSBAUER; CO-57; SITES;

D O I：

10.1007/BF00617472

中图分类号：

O59 [应用物理学];

学科分类号：

摘要：

The dynamics of the Cu-O chain in YBa2Cu3O7-delta was investigated by emission Mossbauer spectroscopy, using Co-57 dopant to microprobe the Cu(1) site. The transformation of the 5-coordinate trigonal-bipyramidal cobalt configuration (species B) to a square-pyramidal one (species C) is induced by the zig-zag motion of the chain. The thermodynamical parameters associated with this conversion were determined, DELTA-H0 = 38 +/- 5 kJ/mol (0.4 eV) and DELTA-S0 = 127 +/- 20 J/K. About 40% of species C does not convert into B at all. We suggest that the inconvertible C has a static square-pyramidal configuration at twin-boundaries where the chain motion is damped. In the Fe-57-doped compound, the iron atoms form linear clusters, and the Cu-O chain motion and also the B-to-C conversion is retarded in the temperature range 200-350 K. A new minor Co species similar to B (namely, B') is reported, which is presumably situated on the grain boundaries. Its nonmetallic environment is reflected in the relatively large value of isomer shift. The properties of the electric field gradient tensor at major Co(Fe) sites are also discussed.

引用

页码：433 / 440

页数：8

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