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Effect of Ni doping on vortex pinning in CaK (Fe1−x Nix)4As4 single crystals
Ames Laboratory Accepted Manuscripts
  • N. Haberkorn, Ames Laboratory and Centro Atómico Bariloche and Instituto Balseiro, CNEA
  • Mingyu Xu, Iowa State University and Ames Laboratory
  • William R. Meier, Iowa State University and Ames Laboratory
  • J. Schmidt, Ames Laboratory and Universidad de Buenos Aires
  • Sergey L. Bud’ko, Iowa State University and Ames Laboratory
  • Paul C. Canfield, Iowa State University and Ames Laboratory
Publication Date
Ames Laboratory; Physics and Astronomy
Report Number
IS-J 10028
Journal Title
Physical Review B

We study the correlation between chemical composition and vortex dynamics in Ni-doped CaK(Fe1−xNix)4As4 (x=0, 0.015, 0.025, 0.03, and 0.05) single crystals by performing measurements of the critical current densities Jc and the flux creep rates S. The magnetic relaxation of all the crystals is well described by the collective creep theory. The samples display a glassy exponent μ within the predictions for vortex bundles in a weak pinning scenario and relatively small characteristic pinning energy (U0<100K). The undoped crystals display modest Jc values at low temperatures and high magnetic fields applied along the c axis. Jc(T) dependences at high fields display an unusual peak. The enhancement in Jc(T) matches with an increase in U0 and the appearance of a second peak in the magnetization. As Ni doping increases, whereas there is a monotonic decrease in Tc there is a nonmonotonic change in Jc. Initially Jc increases, reaching a maximum value for x=0.015, and then Jc decreases for x≥0.025. This change in Jc(x) is coincident with the onset of antiferromagnetic order. The magnetic field dependence of Jc(H) also manifests a change in behavior between these x values. The analysis of the vortex dynamics for small and intermediate magnetic fields shows a gradual evolution in the glassy exponent μ with Ni content, x. This implies that there is no appreciable change in the mechanism that determines the vortex relaxation.

DOE Contract Number(s)
AC02-07CH11358; GBMF4411
Iowa State University Digital Repository, Ames IA (United States)
Citation Information
N. Haberkorn, Mingyu Xu, William R. Meier, J. Schmidt, et al.. "Effect of Ni doping on vortex pinning in CaK (Fe1−x Nix)4As4 single crystals" Vol. 100 Iss. 6 (2019) p. 064524
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