NMR studies of the incommensurate helical antiferromagnet EuCo_2P_2: Determination of antiferromagnetic propagation vector

摘要

Recently, Q.-P. Ding et al. [Phys. Rev. B 95, 184404 (2017)] reported that their nuclear magnetic resonance (NMR) study on EuCo_2As_2 successfully characterized the antiferromagnetic (AFM) propagation vector of the incommensurate helix AFM state, showing that NMR is a unique tool for determination of the spin structures in incommensurate helical AFMs. Motivated by this work, we have carried out ~(153)Eu, ~(31)P, and ~(5)9Co NMR measurements on the helical antiferromagnet EuCo2P2 with an AFM ordering temperature T_N = 66.5 K. An incommensurate helical AFMstructurewas clearly confirmed by ~(153)Eu and ~(31)PNMRspectra on single-crystalline EuCo_2P_2 in zero magnetic field at 1.6 K and its external magnetic field dependence. Furthermore, based on ~(59)Co NMRdata in both the paramagnetic and incommensurateAFMstates,we have determined the model- independent value of the AFM propagation vector k = (0,0,0.73 ± 0.09)2π/c, where c is the c-axis lattice parameter. The temperature dependence of k is also discussed.