On the Origin of Enhanced Critical Current Density and Thermal-Activated Flux Flow in K{sub x}Fe{sub 2−y}Se{sub 2} Superconductors: the Effect of Quenching and Mn Doping

Journal Article · Wed Aug 15 00:00:00 EDT 2018 · Journal of Superconductivity and Novel Magnetism

DOI:https://doi.org/10.1007/S10948-017-4525-3· OSTI ID:22782477

Fang, Y. F., E-mail: [e-mail]; Li, M. T., E-mail: [e-mail] ^[1]

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1. Shanghai University, Department of Physics (China)

A magnetotransport, vortex pinning, and critical current density study of superconducting K{sub 0.8}Fe{sub 2−z}Mn{sub z}Se{sub 2} (z = 0, 0.02) single crystals is reported. The parameters of upper critical field, coherence length, and anisotropic ratio at 0 K are presented. Based on thermally activated flux flow model, the values of pinning potential, U{sub 0}{sup ∥{sub c}}(U{sub 0}{sup ∥{sub a}{sub b}}), at 0.25 T are derived to be as large as 1.3 × 10{sup 4}(1.8 × 10{sup 4}) K for z = 0.02, which shows rather robust and retains still larger than pure ones up to 9 T. Utilizing scanning electron microscope, it is revealed the increased magnitude of magnetic moment in magnetic hysteresis loops correlates well with the crystal morphology variation. The evidence on the inhomogeneous distribution of Mn dopants between the matrix and stripe phase is also shown. Furthermore, the temperature dependence of critical current density is analyzed by different pinning regimes and the model of granular superconductor. It is demonstrated that the Josephson coupling between superconducting grains exists in quenched K{sub 0.8}Fe{sub 2−y}Se{sub 2}. However, for Mn-doped sample, the Mn dopant can induce strong vortex pinning in the form of fine K–Mn–Se inclusions.

• OSTI ID: 22782477
• Journal Information: Journal of Superconductivity and Novel Magnetism, Vol. 31, Issue 8; Other Information: Copyright (c) 2018 Springer Science+Business Media, LLC, part of Springer Nature; http://www.springer-ny.com; Country of input: International Atomic Energy Agency (IAEA); ISSN 1557-1939
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANISOTROPY
COHERENCE LENGTH
CRITICAL CURRENT
CRITICAL FIELD
DOPED MATERIALS
FLOW MODELS
IRON COMPOUNDS
MAGNETIC MOMENTS
MANGANESE ADDITIONS
MONOCRYSTALS
POTASSIUM COMPOUNDS
SCANNING ELECTRON MICROSCOPY
SELENIUM COMPOUNDS
SUPERCONDUCTORS
TEMPERATURE DEPENDENCE