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Mössbauer study of the Eu substitution in (Tl,Pb)-1212 superconductors

✍ Scribed by E. Kuzmann; Z. Klencsár; Á. Sasvári; Z. Homonnay; M. Mair; A. Vértes

Publisher
Elsevier Science
Year
2005
Tongue
English
Weight
226 KB
Volume
420
Category
Article
ISSN
0921-4534

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✦ Synopsis

Eu-substituted (Tl 0.6 Pb 0.4 )(Sr 0.9 Ba 0.1 ) 2 (Ca 1Àx Eu x )Cu 2 O y , for x = 0.2, 0.4, and 0.6 compounds were prepared and investigated by 151 Eu Mo ¨ssbauer spectroscopy, XRD, SEM, EDAX and electrical resistance measurements. The 151 Eu isomer shift reflected trivalent Eu in all cases, but it decreased with increasing Eu content. The monotonous change of the principal component, V zz of electric field gradient with Eu content can be attributed mainly to the change in the lattice parameters due to substitution of Eu for Ca. The correlation between the 151 Eu isomer shift and the superconducting critical temperature supports the hole filling mechanism (and change in the formal valence state of copper) to explain the suppression of superconductivity upon Eu substitution in this system.

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✍ Prem P. Vaishnava; Carl D. Nelson; William P. Pratt Jr.; Punit Boolchand 📂 Article 📅 1990 🏛 Elsevier Science 🌐 English ⚖ 331 KB

l5l-Eu MOssbauer Effect measurements have been performed on the title superconductor at 78 K. The quadrupole coupling constant ( -168 + 14 MHz) is found to be small and negative. The isomer shift ( 0.78 + .03 rom/s relative to EUF3) implies that Eu is trivalent in the compound.