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arXiv · 1704.06293

NMR Determination of an Incommensurate Helical Antiferromagnetic Structure in EuCo2As2

Q. -P. Ding·N. Higa·N. S. Sangeetha·D. C. Johnston·Y. Furukawa
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Abstract

We report $^{153}$Eu, $^{75}$As and $^{59}$Co nuclear magnetic resonance (NMR) results on EuCo$_2$As$_2$ single crystal. Observations of $^{153}$Eu and $^{75}$As NMR spectra in zero magnetic field at 4.3 K below an antiferromagnetic (AFM) ordering temperature $T_{\rm N}$ = 45 K and its external magnetic field dependence clearly evidence an incommensurate helical AFM structure in EuCo$_2$As$_2$. Furthermore, based on $^{59}$Co NMR data in both the paramagnetic and the incommensurate AFM states, we have determined the model-independent value of the AFM propagation vector ${\bf k}$ = (0, 0, 0.73 $\pm$ 0.07)2$π$/$c$ where $c$ is the $c$ lattice parameter. Thus the incommensurate helical AFM state was characterized by only NMR data with model-independent analyses, showing NMR to be a unique tool for determination of the spin structure in incommensurate helical AFMs.

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Q. -P. Ding, N. Higa, N. S. Sangeetha, D. C. Johnston, Y. Furukawa. 2017-04-20. NMR Determination of an Incommensurate Helical Antiferromagnetic Structure in EuCo2As2. https://doi.org/10.1103/physrevb.95.184404

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