Quasielastic and Inelastic Neutron Scattering on RbNiCl3

Quasielastic and inelastic neutron scattering experiments on S =1 quasi 1-D Heisenberg antiferromagnet, RbNiCl 3 were performed. The temperature dependence of the spin correlation length suggests a finite 1-D correlation even at T =0 (K). The dispersion relation in the 3-D ordered phase can be well described by the phenomenological theory of a quasi 1-D Heisenberg antiferromagnet including the Haldane effect. Our results support early works on CsNiCl 3 suggesting the influence of the novel quantum effect even in 3-D ordered phase of the quasi 1-D, S =1 Heisenberg antiferromagnet.