Upper critical magnetic field in Ba_0.68K_0.32Fe_2As_2 and Ba(Fe_0.93Co_0.07)_2As_2

Abstract

We report measurements of the temperature dependence of the radio-frequency magnetic penetration depth in Ba_0.68K_0.32Fe_2As_2 and Ba(Fe_0.93Co_0.07)_2As_2 single crystals in pulsed magnetic fields up to 60 T. From our data, we construct an H-T phase diagram for the inter-plane (H || c) and in-plane (H || ab) directions for both compounds. For both field orientations in Ba_0.68K_0.32Fe_2As_2, we find a concave curvature of the Hc2(T) lines with decreasing anisotropy and saturation towards lower temperature. Taking into account Pauli spin paramagnetism we can describe Hc2(T) and its anisotropy. In contrast, we find that Pauli paramagnetic pair breaking is not essential for Ba(Fe_0.93Co_0.07)_2As_2. For this electron-doped compound, the data support a Hc2(T) dependence that can be described by the Werthamer Helfand Hohenberg model for H || ab and a two-gap behavior for H || c.

7 pages, 8 figures

References in corpus (8)

• To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report
• Nearly Isotropic superconductivity in (Ba,K)Fe2As2
• Vortex phase diagram of Ba(Fe0.93Co0.07)2As2 single crystals
• Determination of anisotropic Hc2 up to 60 T in (Ba0.55K0.45)Fe2As2 single crystals
• Electronic structure of heavily electron-doped BaFe${}_{1.7}$Co${}_{0.3}$As${}_2$ studied by angle-resolved photoemission
• Anisotropic upper critical field and a possible Fulde-Ferrel-Larkin-Ovchinnikov state in a stoichiometric pnictide superconductor LiFeAs
• Universality of superconducting gaps in overdoped Ba0.3K0.7Fe2As2 observed by angle-resolved photoemission spectroscopy
• Electron transport and anisotropy of the upper critical magnetic field in a Ba0.68K0.32Fe2As2 single crystals

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