Comparison of paramagnetic- and nonmagnetic-impurity effects on superconductivity inNd1.85Ce0.15CuO4
| Autor: | Hirose Yamauchi, Jun Sugiyama, Shoji Tanaka, Shinya Tokuono, Shin-Ichi Koriyama |
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| Rok vydání: | 1991 |
| Předmět: | |
| Zdroj: | Physical Review B. 43:10489-10495 |
| ISSN: | 1095-3795 0163-1829 |
| DOI: | 10.1103/physrevb.43.10489 |
| Popis: | The effects of substitution of Co, Ni, or Zn for Cu in the electron-doped superconductors, Nd{sub 1.85}Ce{sub 0.15}Cu{sub 1{minus}{ital x}M{ital x}}O{sub 4} (with {ital M}=Co, Ni, or Zn, {ital x}{le}0.05), have been investigated by powder x-ray diffraction analysis and resistivity, magnetic-susceptibility, and Hall-coefficient measurements. It is observed that only 0.7% Co or 0.8% Ni substitution for Cu destroys superconductivity. On the contrary, for the Zn-substituted samples, it is observed that {ital T}{sub {ital c}} decreases proportionally to {ital x} and the magnitude of {ital T}{sub {ital c}} is {similar to}9 K even for the 2% Zn-substituted sample. This result suggests that the pair-breaking effect plays a dominant role in the suppression of superconductivity in the Co- or Ni-substitute samples. The absolute values of the exchange-interaction energy between an electron and a Co ion and of that between an electron and a Ni ion are estimated at {similar to}0.09 and {similar to}0.08 eV, respectively. These values are comparable to those of the conventional BCS-type superconductors containing paramagnetic impurities. Both the absolute value of the Hall coefficient ({vert bar}{ital R}{sub {ital H}}{vert bar}) and its temperature coefficient ({ital d}{vert bar}{ital R}{sub {ital H}}{vert bar}/{ital dT}) are found to decrease as {ital x}more » increases for all the samples at temperatures higher than 120 K. However, for the Co-substituted samples, it is clearly observed that {vert bar}{ital R}{sub {ital H}}{vert bar} increases proportionally to {ital x} at 30 K, while {vert bar}{ital R}{sub {ital H}}{vert bar} decreases monotonically with increasing {ital x} for the Ni- or Zn-substitute samples. Therefore, it seems that there are no clear relations between the temperature dependence of {ital R}{sub {ital H}} and the suppression in the magnitude of {ital T}{sub {ital c}} due to the substitutional effects.« less |
| Databáze: | OpenAIRE |
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