| Co-Investigator(Kenkyū-buntansha) |
SAITO Takahito the University of Tokushima, Faculty of Integrated Arts and Sciences, Research A, 総合科学部, 助手 (60201505)
MIZUNO Kiyoshi the University of Tokushima, Faculty of Integrated Arts and Sciences, Professor, 総合科学部, 教授 (40087094)
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| Research Abstract |
The Pr content x dependence of the superconducting transition temperature Tc is examined for various oxygen concentrations in R_<1-x>Pr_xBa_2Cu_3O_<7-y>, where R is Nd, Gd, Ho, Y and Yb. In the case of R*Nd, ionic radii of which are smaller than that of Pr, the initial rates of decrease of Tc by Pr substitution (-dTc/dx) decrease with decreasing oxygen concentration for 6.6<7-y<7.0, then becomes constant for 7-y<6.6. The -dTc/dx in the heavily Pr-doped region is larger than that in the initial one, and coinsides wiht that in the case of R=Nd. In contrast, the -dTc/dx in the case of R=Nd, ion radius of which is nearly the same as that of Pr, does not depend upon not only the oxygen concentration but also the Pr content. The weakened Tc-suppression by Pr in the case of R*Nd is explained by considering the hole transfer from the Cu (1) O chain to the Cu (2) O_2 plane. The hole transfer from the Cu (1) O chain to the Cu (2) O_2 plane is caunsidered to be caused by the local distortion in the position of apical oxygen on accout of the substitution of large Pr ion to the small Y ion site. This hole transfer by Pr substitution is similar to that by oxygen deficiency, but the direction of transfer is the opposite with each other.
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