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تسجيل مستخدم جديدLower Critical Field, Anisotropy, and Two-Gap Features of LiFeAs
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K. Sasmal
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The magnetic properties of LiFeAs, as single crystalline and polycrystalline samples, were investigated. The lower critical field deduced from the vortex penetration of two single crystals appears to be almost isotropic with a temperature dependence closer to that of two-gap superconductors. The parameters extracted from the reversible magnetizations of sintered polycrystalline samples are in good agreement with those from the single crystal data.
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The upper critical field $mu_0H_{c2}(T_c)$ of LiFeAs single crystals has been determined by measuring the electrical resistivity using the facilities of pulsed magnetic field at Los Alamos. We found that $mu_0H_{c2}(T_c)$ of LiFeAs shows a moderate a
nisotropy among the layered iron-based superconductors; its anisotropic parameter $gamma$ monotonically decreases with decreasing temperature and approaches $gammasimeq 1.5$ as $Trightarrow 0$. The upper critical field reaches 15T ($Hparallel c$) and 24.2T ($Hparallel ab$) at $T=$1.4K, which value is much smaller than other iron-based high $T_c$ superconductors. The temperature dependence of $mu_0H_{c2}(T_c)$ can be described by the Werthamer-Helfand-Hohenberg (WHH) method, showing orbitally and (likely) spin-paramagnetically limited upper critical field for $Hparallel c$ and $Hparallel ab$, respectively.
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