HIGH-TEMPERATURE SPIN DYNAMICS IN THE S=1 2 SPIN LADDER (VO)(2)P2O7 STUDIED BY P-31 NMR/

We have observed a marked frequency (omega) dependence of the P-31 nuc lear spin-lattice relaxation rate 1/T-1 in the spin-1/2 two-leg ladder compound (VO)(2)P2O7 at temperatures well above the spin gap. The 1/T -1 is found to show an omega(-1/2) dependence above a certain cutoff f requency, indicating one-dimensional diffusive spin dynamics along the leg of ladders. We have also found that the spin-diffusion constant i ncreases rapidly with decreasing temperature. This may be related to t he increase of the antiferromagnetic correlation length within the lad der at low temperatures.