OXIDATION-STATE AND SUPERCONDUCTING PROPERTIES OF Y1-XPRXSR2CU2.85RE0.15O7+DELTA

Citation
M. Murugesan et al., OXIDATION-STATE AND SUPERCONDUCTING PROPERTIES OF Y1-XPRXSR2CU2.85RE0.15O7+DELTA, Journal of applied physics, 80(12), 1996, pp. 6884-6887
Citations number
33
Categorie Soggetti
Physics, Applied
Journal title
ISSN journal
00218979
Volume
80
Issue
12
Year of publication
1996
Pages
6884 - 6887
Database
ISI
SICI code
0021-8979(1996)80:12<6884:OASPOY>2.0.ZU;2-G
Abstract
Superconductivity exists in orthorhombic Y1-xPrxSr2Cu2.85Re0.15O7+delt a up to a critical concentration (x(cr)) of 0.65. A progressive decrea se in T-c occurs as x increases from 0 to 0.65. A further increase in x leads to a tetragonal transformation and as a consequence the Ti van ishes; however, the orthorhombicity of these Sr-based compounds is muc h lower than that observed for the Ba analog, Y1-xPrxBa2Cu3O7-delta an d, hence, the T-c. On the one hand, crystal chemistry correlations ind icate that the Pr ion is in trivalent state while on the other hand, t he stabilizing cation, viz., Re, is in hexavalent state which accounts for the excess oxygen (>7.0) in the system, The high x(cr) value of t he Sr series compared to the Pa series (x(cr)=0.55) is attributed to t he much reduced orbital overlap of the trivalent Pr(4f) state with the Cu(3d(x2-y2))-O(2p) conduction band, via hole localization and/or pai r breaking, and is not due to the much discussed hole filling by tetra valent Pr. (C) 1996 American Institute of Physics.