51V-NMR study of the quasi-one-dimensional antiferromagnet BaCo2V2O8

We have investigated the magnetic properties of quasi-one-dimensional antiferromagnet BaCo2V2O8 by the measurements of 51V-NMR spectrum. With decreasing temperature, K‖ shows a broad peak around 30 K signaling the 1D short-range order in the Co2+ spin chain. The estimated Weiss temperature θ = −105 K, hyperfine coupling constants Ahf‖ = 2.1 kOe/µB for H ‖ c and Ahf⊥ = 2.6 kOe/µB for H ⊥ c at 13 kOe are comparable to those at 70.6 kOe. These results suggest that static magnetic properties in the paramagnetic state are nearly independent of external magnetic field, although the ground Néel state is suppressed by the application of external magnetic field above Hc = 39 kOe along c-axis. In the antiferromagnetic state below TN = 5.4 K, the double rectangle-like powder pattern was observed, indicating two V sites exposed to different size of internal fields, HA1 = 2.1 and HA2 = 3.8 kOe. The internal fields at V sites are explained by taking into account of the classical and pseudo-dipolar fields from Co2+ magnetic moments.