Publication Date

8-1-2019

Department

Ames Laboratory; Physics and Astronomy

Campus Units

Ames Laboratory, Physics and Astronomy

OSTI ID+

1561964

Report Number

IS-J 10028

DOI

10.1103/PhysRevB.100.064524

Journal Title

Physical Review B

Volume Number

100

Issue Number

6

First Page

064524

Abstract

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

Language

en

Publisher

Iowa State University Digital Repository, Ames IA (United States)

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