High superconducting anisotropy and weak vortex pinning in Co doped LaFeAsO
| Autor: | Haidong Zhou, Gang Li, Luis Balicas, R. W. McCallum, Gael Grissonnanche, Jiaqiang Yan, T.A. Lograsso |
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| Jazyk: | angličtina |
| Rok vydání: | 2012 |
| Předmět: |
Physics
Superconductivity Condensed matter physics Condensed Matter - Superconductivity Doping FOS: Physical sciences 02 engineering and technology 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Electronic Optical and Magnetic Materials Vortex Magnetic field Superconductivity (cond-mat.supr-con) Condensed Matter::Superconductivity 0103 physical sciences Cuprate 010306 general physics 0210 nano-technology Anisotropy Co doped Phase diagram |
| Popis: | Here, we present an electrical transport study in single crystals of LaFe$_{0.92}$Co$_{0.08}$AsO ($T_c \simeq 9.1$ K) under high magnetic fields. In contrast to most of the previously reported Fe based superconductors, and despite its relatively low $T_c$, LaFe$_{1-x}$Co$_x$AsO shows a superconducting anisotropy which is comparable to those seen for instance in the cuprates or $\gamma_H = H_{c2}^{ab}/H_{c2}^{c} = m_c/m_{ab} \simeq 9$, where $m_c/m_{ab}$ is the effective mass anisotropy. Although, in the present case and as in all Fe based superconductors, $\gamma \rightarrow 1$ as $T \rightarrow 0$. Under the application of an external field, we also observe a remarkable broadening of the superconducting transition particularly for fields applied along the inter-planar direction. Both observations indicate that the low dimensionality of LaFe$_{1-x}$Co$_x$AsO is likely to lead to a more complex vortex phase-diagram when compared to the other Fe arsenides and consequently, to a pronounced dissipation associated with the movement of vortices in a possible vortex liquid phase. When compared to, for instance, F-doped compounds pertaining to same family, we obtain rather small activation energies for the motion of vortices. This suggests that the disorder introduced by doping LaFeAsO with F is more effective in pinning the vortices than alloying it with Co. Comment: 7 figures, 7 pages, Phys. Rev. B (in press) |
| Databáze: | OpenAIRE |
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