Effects of Co substitution on thermodynamic and transport properties and anisotropic Hc2 in Ba(Fe1-xCox)2As2 single crystals

被引:509
作者
Ni, N. [1 ,2 ]
Tillman, M. E. [1 ,2 ]
Yan, J. -Q. [1 ,2 ]
Kracher, A. [1 ,2 ]
Hannahs, S. T. [3 ]
Bud'ko, S. L. [1 ,2 ]
Canfield, P. C. [1 ,2 ]
机构
[1] US DOE, Ames Lab, Ames, IA 50011 USA
[2] Iowa State Univ, Dept Phys & Astron, Ames, IA 50011 USA
[3] Natl High Magnet Field Lab, Tallahassee, FL 32310 USA
关键词
barium compounds; cobalt compounds; electrical resistivity; iron compounds; magnetic transitions; phase diagrams; phase separation; solid-state phase transformations; superconducting critical field; superconducting materials; thermodynamic properties;
D O I
10.1103/PhysRevB.78.214515
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
Single crystalline samples of Ba(Fe1-xCox)(2)As-2 with x < 0.12 have been grown and characterized via microscopic, thermodynamic, and transport measurements. With increasing Co substitution, the thermodynamic and transport signatures of the structural (high-temperature tetragonal to low-temperature orthorhombic) and magnetic (high-temperature nonmagnetic to low-temperature antiferromagnetic) transitions are suppressed at a rate of roughly 15 K/% Co. In addition, for x >= 0.038 superconductivity is stabilized, rising to a maximum T-c of approximately 23 K for x approximate to 0.07 and decreasing for higher x values. The T-x phase diagram for Ba(Fe1-xCox)(2)As-2 indicates that either superconductivity can exist in both low-temperature crystallographic phases or that there is a structural phase separation. Anisotropic superconducting upper critical-field data [H-c2(T)] show a significant and clear change in anisotropy between samples that have higher temperature structural phase transitions and those that do not. These data show that the superconductivity is sensitive to the suppression of the higher temperature phase transition.
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