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arXiv · 1005.3965

Intergrain effects in the AC susceptibility of polycrystalline LaFeAsO_{0.94}F_{0.06}: comparison with cuprate superconductors

G. Bonsignore·A. Agliolo Gallitto M. Li Vigni·J. L. Luo·G. F. Chen·N. L. Wang·D. V. Shovkun
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Abstract

The AC susceptibility at zero DC magnetic field of a polycrystalline sample of LaFeAsO_{0.94}F_{0.06} (T_c = 24 K) has been investigated as a function of the temperature, the amplitude of the AC magnetic field (in the range Hac = 0.003 - 4 Oe) and the frequency (in the range f = 10 kHz - 100 kHz). The temperature dependence of the AC susceptibility exhibits the typical two-step transition arising from the combined response of superconduncting grains and intergranular weak-coupled medium. The intergranular part of the susceptibility strongly depends on both the amplitude and the frequency of the AC driving field, from few Kelvin below T_c down to T = 4.2 K. Our results show that, in the investigated sample, the intergrain critical current is not determined by pinning of Josephson vortices but by Josephson critical current across neighboring grains.

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G. Bonsignore, A. Agliolo Gallitto M. Li Vigni, J. L. Luo, G. F. Chen, N. L. Wang, D. V. Shovkun. 2010-05-21. Intergrain effects in the AC susceptibility of polycrystalline LaFeAsO_{0.94}F_{0.06}: comparison with cuprate superconductors. https://doi.org/10.1016/j.physc.2010.11.006

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