Effect of Ni doping on vortex pinning in $\mathrm{CaK}{\left(\mathrm{F}{\mathrm{e}}_{1-x}\mathrm{N}{\mathrm{i}}_x\right)}_4\mathrm{A}{\mathrm{s}}_4$ single crystals

Journal Article · 28 August 2019 · Physical Review B

DOI: https://doi.org/10.1103/PhysRevB.100.064524 · OSTI ID:1561964

Haberkorn, N.  ^[1]; Xu, M. ^[2]; Meier, W. R. ^[2]; Schmidt, J.  ^[3]; Bud’ko, S. L. ^[2]; Canfield, P. C. ^[2]

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1. Ames Lab. and Iowa State Univ., Ames, IA (United States); Centro Atómico Bariloche and Instituto Balseiro (Argentina)
2. Ames Lab. and Iowa State Univ., Ames, IA (United States)
3. Ames Lab. and Iowa State Univ., Ames, IA (United States); Univ. de Buenos Aires, Buenos Aires (Argentina)

We study the correlation between chemical composition and vortex dynamics in Ni-doped CaK(Fe_1–xNi_x)₄As₄ (x = 0, 0.015, 0.025, 0.03, and 0.05) single crystals by performing measurements of the critical current densities J_c 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 J_c values at low temperatures and high magnetic fields applied along the c axis. J_c(T) dependences at high fields display an unusual peak. The enhancement in J_c(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 T_c there is a nonmonotonic change in J_c. Initially J_c increases, reaching a maximum value for x = 0.015, and then J_c decreases for x ≥ 0.025. This change in J_c(x) is coincident with the onset of antiferromagnetic order. The magnetic field dependence of J_c(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. As a result, this implies that there is no appreciable change in the mechanism that determines the vortex relaxation.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-07CH11358; GBMF4411
• OSTI ID: 1561964
• Alternate ID(s): OSTI ID: 1559358
• Report Number(s): IS-J-10028; PRBMDO; TRN: US2000672
• Journal Information: Physical Review B, Vol. 100, Issue 6; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English