17O NMR study of the triangular lattice antiferromagnet CuCrO2

The single crystalline and powder samples of multiferroic CuCrO2 have been investigated by 17O NMR techniques in the paramagnetic and magnetically ordered states. The unusual negative hyperfine field on oxygen nuclei, Hhf = −5.2 kOe/µB, has been determined in paramagnetic state. The 17O NMR spectrum in ordered state has a shape typical for incommensurate magnetic structure. It can be well described taking into account only dipole fields which are produced by Cr3+-ions with magnetic moment μ = 2.2 μB. The parameters of the EFG (electric field gradient) tensor - the quadrupole frequency (νQ) and the asymmetry parameter, have been determined. The value of νQ increases monotonously with decreasing temperature in the range 90 K > T > 1.5 K. The estimates of the population of the ligands p - orbitals have been obtained.