Physical Review B
We report 153Eu, 75As, and 59Co nuclear magnetic resonance (NMR) results on EuCo2As2 single crystal. Observations of 153Eu and 75As NMR spectra in zero magnetic field at 4.3 K below an antiferromagnetic (AFM) ordering temperature TN=45 K and its external magnetic field dependence clearly evidence an incommensurate helical AFM structure in EuCo2As2. Furthermore, based on 59CoNMR data in both the paramagnetic and the incommensurate AFM states, we have determined the model-independent value of the AFM propagation vector k=(0,0,0.73±0.07)2π/c, where c is the clattice 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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