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Abstract

As-75 NMR measurements were performed on a polycrystalline sample of spin-1/2 alternating spin chain Heisenberg antiferromagnet AgVOAsO4. The temperature-dependentNMRshiftK(T), which is a direct measure of the intrinsic spin susceptibility, agrees very well with the spin-1/2 alternating-chain model, justifying the assignment of the spin lattice. From the analysis of K(T), magnetic exchange parameters were estimated as follows: the leading exchange J/k(B) similar or equal to 38.4 K and the alternation ratio alpha= J'/J similar or equal to 0.69. The transferred hyperfine coupling between the As-75 nucleus and V4+ spins obtained by comparing the NMR shift with the bulk susceptibility amounts to A(hf) similar or equal to 3.3 T mu B. The effect of interchain couplings on the low-temperature activated behavior of K(T) and the spin-lattice relaxation rate 1/T-1 is identified.