Campus Units

Physics and Astronomy, Ames Laboratory

Document Type

Article

Publication Version

Published Version

Publication Date

11-1-2015

Journal or Book Title

Physical Review B

Volume

92

Issue

18

First Page

184504

DOI

10.1103/PhysRevB.92.184504

Abstract

We report 75As nuclear magnetic resonance (NMR) measurements of single-crystalline Ca(Fe1−xCox)2As2 (x=0.023, 0.028, 0.033, and 0.059) annealed at 350∘C for 7 days. From the observation of a characteristic shape of 75As NMR spectra in the stripe-type antiferromagnetic (AFM) state, as in the case of x=0 (TN=170 K), clear evidence for the commensurate AFM phase transition with the concomitant structural phase transition is observed in x=0.023 (TN=106 K) and x=0.028 (TN=53 K). Through the temperature dependence of the Knight shifts and the nuclear spin lattice relaxation rates (1/T1), although stripe-type AFM spin fluctuations are realized in the paramagnetic state as in the case of other iron pnictide superconductors, we found a gradual decrease of the AFM spin fluctuations below a crossover temperature T∗ that was nearly independent of Co-substitution concentration, and it is attributed to a pseudogaplike behavior in the spin excitation spectra of these systems. The T∗ feature finds correlation with features in the temperature-dependent interplane resistivity, ρc(T), but not with the in-plane resistivity ρa(T). The temperature evolution of anisotropic stripe-type AFM spin fluctuations is tracked in the paramagnetic and pseudogap phases by the 1/T1 data measured under magnetic fields parallel and perpendicular to the c axis. Based on our NMR data, we have added a pseudogaplike phase to the magnetic and electronic phase diagram of Ca(Fe1−xCox)2As2.

Comments

This article is published as Cui, J., B. Roy, M. A. Tanatar, S. Ran, S. L. Bud'ko, R. Prozorov, P. C. Canfield, and Y. Furukawa. "Antiferromagnetic spin correlations and pseudogaplike behavior in Ca (Fe 1− x Co x) 2 As 2 studied by As 75 nuclear magnetic resonance and anisotropic resistivity." Physical Review B 92, no. 18 (2015): 184504. DOI: 10.1103/PhysRevB.92.184504. Posted with permission.

Copyright Owner

American Physical Society

Language

en

File Format

application/pdf

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