QUASI-1D ANTIFERROMAGNETS WITH S=1 AND S=3 2 - THE ISOSTRUCTURAL COMPOUNDS AGVP2S6 AND AGCRP2S6/

Time-of-flight inelastic scattering from polycrystalline samples of Ag VP2S6 and AgCrP2S6 has revealed characteristic features of integer and half-integer spin antiferromagnetic chains. In the S = 1 system we ha ve followed the temperature dependence of the Haldane-gap mode in a wi de temperature range, The staggered susceptibility compares well with numerical calculations and confirms the exchange-energy scale determin ed earlier. The spin-wave velocity of the S = 3/2 system suggests a cl ose resemblance to the S = ? case.