Browsing by Author "Hong, IP"

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Contributions of CuO2 planes and CuO chains on the transport properties of YBa2Cu4O8
(1999-01-20)
Chatterjee, S
;
Weng, SS
;
Hong, IP
;
Chang, CF
;
Yang, HD
We have investigated the contributions of CuO2 planes and CuO chains on the transport properties of YBa2Cu4O8 by measuring the electrical resistivity and thermoelectric power (S) of Y1-xPrxBa2(Cu1-yZny)(4)O-8, Y1-xCaxBa2Cu4O8 and YBa2(Cu1-xGax)(4)O-8. Pr reduces the mobile carrier concentration in the CuO2 planes in YBa2Cu4O8, as a consequence, the superconducting transition temperature is progressively decreased with increasing Pr. The S(T) data suggest that the metallic behavior at lower temperature of the Pr and Zn doped compounds is contributed by the double CuO chains. On the other hand, the S(T) behavior of Ca doped samples is opposite to that of the Pr doped samples because the doping of Ca in Y-site introduces holes in the CuO2 planes. However, the substitution of Ga in Cu(1)-site suppresses the carrier concentration in CuO chains and increases the normal-state resistivity revealing the important contribution from CuO chains on the metallic behavior of YBa2Cu4O8 and PrBa2Cu4O8. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
Origin of size effect on superconductivity in (R-0.8 Pr-0.2)Ba2Cu3O7 studied by soft X-ray absorption spectroscopy
(2001-03-30)
Chen, JM
;
Nachimuthu, P
;
Lin, JY
;
Hong, IP
;
Chang, CF
O K-edge X-ray absorption near-edge structure (XANES) spectroscopy of (R-0.8 Pr-0.2)Ba2Cu3O7 (R = Y, Tm, Dy, Gd, Eu and Sm) has been performed to investigate the dependence of hole distribution on ionic size of the R3+ ions. Near the O Is absorption edge, pre-peaks at similar to 527.8 and similar to 528.5 eV are assigned to transitions into O 2p hole states located in the CuO3 ribbons and CuO2 planes, respectively. As deduced from O K-edge X-ray absorption spectra, the hole concentrations in the CuO2 planes decrease monotonically with increasing ionic size of the rare-earth elements. The present XANES results clearly demonstrate that the suppression of superconductivity in (R1-x Pr-x)Ba2Cu3O7 With ionic radius of the R3+ ions results predominantly from the hole-depletion effect. (C) 2001 Elsevier Science B.V. All rights reserved.
Possible evidence for the existence of the Fehrenbacher-Rice band: O K-edge XANES study on Pr1-xCaxBa2Cu3O7
(2002-04-01)
Hong, IP
;
Lin, JY
;
Chen, JM
;
Chatterjee, S
;
Liu, SJ
X-ray absorption near edge structure (XANES), resistivity, and thermoelectric power have been measured on Pr1-xCaxBa2Cu3O7. These data reveal an intriguing electronic structure in Pr-doped cuprates. The absorption peak in XANES associated with the Fehrenbacher-Rice (FR) band has been identified. The Ca-doped holes in Pr1-xCaxBa2Cu3O7 go to both the Zhang-Rice (ZR) and FR bands. Comparative studies on the related samples suggest that the FR band is partially filled and highly localized. Implications of these results on other recent experiments, such as the observation of superconductivity in PrBa2Cu3O7 single crystals, are discussed.
Pr-induced superconductivity suppression in YxPr1-xBa2Cu4O8 probed by soft-X-ray absorption spectroscopy: a comparative studies of YxPr1-xBa2Cu4O8 and YxPr1-xBa2Cu3O7
(2003-03-07)
Chen, JM
;
Liu, SJ
;
Lee, JM
;
Hong, IP
;
Lin, JY
The variation of hole states with Pr doping for YxPr1-x Ba2Cu3O7 and YxPr1-xBa2Cu4O8 has been investigated by O K-edge X-ray absorption spectroscopy. Upon Pr substitution, T-c suppression rate in YxPr1-xBa2Cu4O8 is slower than that in YxPr1-xBa2Cu3O7. For both systems, hole carriers in the CuO2 planes and CuO chains decrease monotonically with increasing Pr doping level. The depletion rate of hole carriers in the CuO2 planes with Pr doping in YxPr1-xBa2Cu4O8 is considerably slower than that in YxPr1-xBa2Cu3O7. The oxygen content affects the depletion rate of hole carriers in cuprates with Pr doping. (C) 2003 Elsevier Science B.V. All rights reserved.
X-ray absorption near-edge structure of Pr1-xBa2+xCu3O7
(2000-11-01)
Yang, HD
;
Hong, IP
;
Chatterjee, S
;
Nachimuthu, P
;
Chen, JM
PrBa2Cu3O7 (Pr123) has attracted much attention due to its non-superconductivity and other anomalies. The very recent reports on superconducting Pr123, instead of putting an end on this issue, virtually stimulate more controversies. One of the proposed explanations for the recently observed superconductivity in Pr123 is that the samples could be Ba-rich Pr123. To investigate this possibility, we have prepared Pr1-xBa2+xCu3O7 With x=0 to 0.3. It is found that resistivity of the samples becomes smaller with increasing x, together with elongation of the c-axis. O K-edge x-ray absorption structure indicates an increase in the carrier concentration with Ba doping. However, carriers are introduced in a peculiar way rather than simply added into CuO2 planes.