QUANTUM EFFECTS IN SPIN DYNAMICS OF QUASI-ONE-DIMENSIONAL ANTIFERROMAGNETS

Some experiments related to the quantum nature of spins that strongly manifest itself in the quasi-one-dimensional antiferromagnets are disc ussed with a reference to CsNiCl3 and related compounds. In particular , the field dependence of the low-temperature staggered magnetization that is substantially reduced by zero-point motion of spins was measur ed by neutron diffraction and is shown to account for the nonlinear ho mogeneous susceptibility. We also present a comparison between the spi n dynamics of S=1 CsNiCl3 and S=5/2 CsMnBr3 above their Neel ordering temperatures measured by inelastic neutron scattering. It provides ano ther spectacular evidence of the fundamental difference between the ch ains of integer and half-integer spins predicted by Haldane.