P31 NMR of trimer cluster compound Sr3Cu3(PO4)4

Abstract P 31 NMR in S = 1 2 linear cluster compound Sr 3 Cu 3 ( PO 4 ) 4 was investigated. At any temperature, the spectrum corresponds to a typical overlap of two powder patterns, consistent with two inequivalent phosporous sites, having different components of the shift parameters. Intra-trimer exchange ( J 1 = 110 ± 5 K ) and hyperfine field ( H hf ) were directly obtained from temperature dependence of K iso , considering S = 1 2 , Heisenberg linear trimer. The behavior of the H hf for the two sites are quite different and reflects the formation of trimers below 100 K. The relaxation rate, 1 / T 1 in the range 100–210 K, shows an activation ( Δ / k B = 43 K ) dependence of the spin excitation.