CL-35 NMR AND RELAXATION IN THE TRIANGULAR LATTICE ANTIFERROMAGNET VCL2

Cl-35 NMR spectra and relaxation measurements in the triangular two-di mensional lattice of VCl2, with antiferromagnetic (AF) interactions be tween V2+ S = 3/2 ions are presented. The spectra are characteristic o f the 1/2 <-> -1/2 central line, broadened by the powder distribution of the second-order quadrupole interaction; the electric field gradien t at the Cl site is derived. For T less-than-or-equal-to T(N) a broade ning of the line due to the onset of the static dipolar field is detec ted. The Cl-35 relaxation is driven by the dipolar hyperfine interacti on with the magnetic ion, and from the temperature dependence of the r elaxation rate, W, information on the correlated V2+, spin dynamics is obtained. The absolute value of W and its temperature dependence for T --> T(N)+ are not consistent with the behaviour expected for convent ional 2D Heisenberg systems. It is argued that peculiar spin dynamics, similar to that related with Z2 vortices, with a possible crossover t o a 3D or a 2D Ising system, may be responsible for these effects.