Browsing by Author "Wang, J.-S."

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Effect of Mn impurities on the superconductivity in NaxCoO2 center dot yH(2)O
(2007-09-01)
Chen, Y.-J.
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Liu, C.-J.
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Wang, J.-S.
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Lin, J.-Y.
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Sun, C. P.
To shed light on the symmetry of the superconducting order parameter in NaxCoO2 center dot yH(2)O, the Mn doping effects are studied. X-ray absorption spectroscopy verifies that the doped Mn impurities occupy the Co sites and are with a valance close to +4. Impurity scattering by Mn is in the unitary limit that, however, does not lead to strong T-c suppression. This absence of the strong impurity effects on T-c is inconsistent with the simple picture of a sign-changing order parameter. Coexistence of the s-wave superconducting order parameter and the nodal one is proposed to reconcile all the existing experiments and has been implied by the specific heat experiments.
Induced magnetic moment by Mn doping in NaxCo1-zMnzO2 center dot yH(2)O
(2007-03-01)
Lin, J.-Y.
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Chen, Y.-J.
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Liu, C.-J.
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Wang, J.-S.
;
Sun, C. P.
Impurity effects on NaxCoO2 (.) yH(2)O are studied by Mn doping. Spectroscopic evidence reveals that the doped Mn ions occupy the Co sites and the valence is +4. The magnetic local moment induced by Mn doping was observed and mu(eff) 3: 20 mB. The induced local moment could lead to magnetic pair-breaking and is likely to be responsible for the Tc suppression by Mn impurities in Na(x)Co(1-z)MnzO(2) (.) yH(2)O. (c) 2006 Elsevier B. V. All rights reserved.
Specific heat of Mn-doped NaxCoO2 center dot yH(2)O
(2007-09-01)
Lin, J.-Y.
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Chen, Y.-J.
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Liu, C.-J.
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Wang, J.-S.
;
Sun, C. P.
C(T) of NaxCo0.99Mn0.01O2 center dot yH(2)O is studied to reveal more details on the nature of the doped Mn ions and the T-c suppression. The extra specific heat contribution in NaxCo0.99Mn0.01O2 center dot yH(2)O manifests the induced local magnetic moment due to Mn doping. The absence of the superconducting transition peak in C(T) of NaxCo0.99Mn0.01O2 center dot yH(2)O suggests a reduced superconducting volume fraction. (C) 2007 Elsevier B.V. All rights reserved.