P31 NMR of trimer cluster compound Sr3Cu3(PO4)4

P31 NMR in S=12 linear cluster compound Sr3Cu3(PO4)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 (J1=110±5K) and hyperfine field (Hhf) were directly obtained from temperature dependence of Kiso, considering S=12, Heisenberg linear trimer. The behavior of the Hhf for the two sites are quite different and reflects the formation of trimers below 100 K. The relaxation rate, 1/T1 in the range 100-210 K, shows an activation (Δ/kB=43K) dependence of the spin excitation.