Synthesis, anisotropy, and superconducting properties of LiFeAs single crystal

Applied Physics Letters (Impact Factor: 3.52). 05/2010; 96(21):212508-212508-3. DOI: 10.1063/1.3435472
Source: arXiv

ABSTRACT A LiFeAs single crystal with Tconset ∼ 19.7 K was grown in a sealed tungsten crucible using the Bridgeman method. The electrical resistivity experiments revealed a ratio of room temperature to residual resistivity of approximately 46 and 18 for the in-plane and out-of plane directions, respectively. The estimated anisotropic resistivity, γρ = ρc/ρab, was approximately 3.3 at Tconset. The upper critical fields had large Hc2∥ab and Hc2∥c values of 83.4 T and 72.5 T, respectively, and an anisotropy ratio is γH = Hc2∥ab/Hc2∥c ∼ 1.15. The high upper critical field value and small anisotropy highlight the potential use of LiFeAs in a variety of applications. The calculated critical current density (Jc) from the M-H loop is approximately 103 A/cm2

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    ABSTRACT: The reversible magnetization curves for various magnetic fields are investigated for a single crystal of the optimally doped NaFe0.97Co0.03As superconductor with the superconducting transition temperature Tc = 20.9 K (ρ(T) = 0) in the case where H is parallel to c-axis. A well-formed rounding effect is observed in the temperature dependence of the magnetization, and it widens on increasing the strength of the applied magnetic fields. At 20.2 K, we observe a crossing of the M(T) curves for different applied magnetic fields, indicating important fluctuation effects. The irreversibility line Hirr(T) obeys a universal scaling relation Hirr(T) = H0(1 − T/Tc)n characterized by n ~ 1.537, which confirms the moderately anisotropic nature of the sample. The scaling analysis of the reversible magnetization in the region near Tc(H) supports the three-dimensional nature of the vortex fluctuations in NaFe0.97Co0.03As.
    Superconductor Science and Technology 11/2014; 27(12):125006. DOI:10.1088/0953-2048/27/12/125006 · 2.80 Impact Factor
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    ABSTRACT: We investigate the critical current density and the lower critical field in a superconducting single crystal. High quality single crystals were grown by the Bridgman method. A sample with a nominal composition of with x = 0.01 showed a of 32 K. A well-formed secondary peak in the specific temperature range was observed in the magnetic hysteresis for and , revealing the anisotropic nature of the flux pinning in the sample. The normalized volume pinning forces at various temperatures followed good fits with the scaling law ∝ ( with p = 1 and q = 2, which predicts the normal point-type pinning in the sample. The vortex phase diagram shows that the irreversibility field , the secondary peak field , and the onset field of the secondary peak follow a universal scaling law H(T) = H(0)(/. The temperature dependence of the superfluid density was fitted well by the two-gap BCS model in the full temperature range using two superconducting gaps, = 8.4 ± 0.5 meV and = 3.1 ± 0.5 meV.
    Superconductor Science and Technology 06/2014; 27(7):075011. DOI:10.1088/0953-2048/27/7/075011 · 2.80 Impact Factor
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    ABSTRACT: The magneto-resistivity and electric field-current density (E-J) curves were investigated up to a magnetic field 9 T in the optimally doped single crystal with a superconducting temperature () of 24.6 K. The E-J Scaling behaviors below and above vortex glass transition temperature () were found, confirming the existence of the vortex glass phase transition. The critical exponents for the diverging spatial and time correlations at , were obtained as v = and z = , respectively. The obtained critical exponents are in good agreement with the predicted values of v ~ 1 - 2 and z > 4 within the 3D vortex glass theory.
    06/2013; 15(2). DOI:10.9714/psac.2013.15.2.016

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