STATIC PROPERTIES OF A QUASI-ONE-DIMENSIONAL ANTIFERROMAGNET IN A MAGNETIC-FIELD

We calculate the effect of zero-point fluctuations on the magnetostati c properties of a quasi-one-dimensional antiferromagnetic helimagnet w ith and without in-plane anisotropy. We find substantial reduction of the uniform susceptibility and the sublattice magnetization from their classical values and appreciable renormalization of the spin-flop fie ld at T=0. The magnetization curve varies nonlinearly at small fields and is described by a universal formula at high fields. The results ar e compared with numerical simulations on one-dimensional systems and m easurements in the CsNiCl3-type compounds.