Charge distribution in Y{sub 1{minus}{ital x}}Pr{sub {ital x}}Ba{sub 2}Cu{sub 3}O{sub 7}: A valency model for the depression of {ital T}{sub {ital c}}
- Advanced Research Laboratory, Toshiba Research and Development Center, 1, Komukai Toshiba-cho, Saiwai-ku, Kawasaki 210 (Japan)
We have carried out an evaluation of cation valences in Y{sub 1{minus}{ital x}}Pr{sub {ital x}}Ba{sub 2}Cu{sub 3}O{sub 7} (YPBCO) on the basis of the fractional-valency ionic crystal model to investigate the causes of {ital T}{sub {ital c}} suppression with Pr doping. Through comparison with the case of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}}, we have quantitatively estimated the extent to which the {ital T}{sub {ital c}} depression can be accounted for in terms of the decrease in hole concentration in the CuO{sub 2} planes, paying special attention to the difference in the fourth ionization potential between Y and Pr. We have found that the valency of Pr is higher than that of Y by about 0.3 in YPBCO, thus reducing the Cu valency in the CuO{sub 2} planes with the Pr substitution, but that this effect can quantitatively explain no more than about one-third of the {ital T}{sub {ital c}} depression. Accordingly, it is suggested that those effects neglected in the present model, such as a further decrease in mobile hole concentration due to the Pr-O hybridization, the localization of carriers due to disorder, and the magnetic pair breaking due to Pr spin, must play an important role in the mechanism of {ital T}{sub {ital c}} suppression in YPBCO.
- OSTI ID:
- 76412
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 52, Issue 1; Other Information: PBD: 1 Jul 1995
- Country of Publication:
- United States
- Language:
- English
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