Universal behavior of one-dimensional gapped antiferromagnets in a staggered magnetic field

We study the properties of one-dimensional gapped Heisenberg antiferromagnets in the presence of a strong staggered magnetic field. For thesesystems we predict a universal form for the staggered magnetization curve. This function, as well as the effect the staggered field has on the energy gaps in longitudinal and transversal excitation spectra, is determined fromthe universal form of the effective potential in O(3)-symmetric(1+1)-dimensional field theory. Our theoretical findings are in excellent agreement with recent neutron scattering data on R₂BaNiO(R=magnetic rare earth) linear-chain mixed spin antiferromagnets.