Browsing by Author "Chen, TK"

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    Doping-driven structural phase transition and loss of superconductivity in MxFe1−xSeδ (M=Mn, Cu)
    (American Physical Society, 2010-09-02) Huang, TW; Chen, TK; Yeh, KW; Ke, CT; Chen, CL; Huang, YL; Hsu, FC; Wu, MK; Wu, PM; Avdeev, M; Studer, AJ
    In this paper, we report the results of detailed studies on Mn and Cu substitution to Fe site of β-FeSe, namely, MnxFe1−xSe1−δ and CuxFe1−xSe1−δ (δ equals to 0.03–0.05 based on our neutron-diffraction refinements). The results show that with only 10 at. % Cu doping the compound becomes a Mott insulator. Detailed temperature-dependent structural analyses of these Mn- and Cu-substituted compounds show that the structural transition, which is associated with the changes in the building block FeSe4 tetrahedron, is essential to the occurrence of superconductivity in β-FeSe. © 2010, American Physical Society
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    Structural phase transition in TmxFe1-xSe0.85 (Tm = Mn and Cu) and its relation to superconductivity
    (arXivLabs, 2009-07-23) Huang, TW; Chen, TK; Yeh, KW; Ke, CT; Chen, CL; Huang, YL; Hsu, FC; Wu, MK; Wu, PM; Avdeev, M; Studer, AJ
    In this letter, we report the results of detailed studies on Mn- and Cu-substitution to Fe-site of beta-FeSe, namely MnxFe1-xSe0.85 and CuxFe1-xSe0.85. The results show that with only 10 at% Cu-doping the compound becomes a Mott insulator. Detailed temperature dependent structural analyses of these Mn- and Cu-substituted compounds show that the structural transition, which is associated with the changes in the building block FeSe4 tetrahedron, is essential to the occurrence of superconductivity in beta-FeSe.
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    Tailoring the coercivity in ferromagnetic ZnO thin films by 3d and 4f elements codoping
    (AIP Scitation, 2014) Lee, JJ; Xing, GZ; Yi, JB; Chen, TK; Ionescu, M; Li, S
    Cluster free, Co (3d) and Eu (4f) doped ZnO thin films were prepared using ion implantation technique accompanied by post annealing treatments. Compared with the mono-doped ZnO thin films, the samples codoped with Co and Eu exhibit a stronger magnetization with a giant coercivity of 1200 Oe at ambient temperature. This was further verified through x-ray magnetic circular dichroism analysis, revealing the exchange interaction between the Co 3d electrons and the localized carriers induced by Eu3+ ions codoping. The insight gained with modulating coercivity in magnetic oxides opens up an avenue for applications requiring non-volatility in spintronic devices. © 2014, AIP Publishing LLC.