Neutron diffraction study of the nuclear and magnetic structure of the quasi-one-dimensional compoundCuSiO3aroundTN=8K

Abstract

We investigated the nuclear and magnetic structure of ${\mathrm{CuSiO}}_{3}$ by neutron powder diffraction methods at room temperature and around ${T}_{N}=8\mathrm{K}.$ With decreasing temperature the lattice parameters showed, similar to ${\mathrm{CuGeO}}_{3},$ decreasing a and b parameters and a slightly increasing c parameter down the chain direction. Below the second order phase transition at ${T}_{N}$ we observed for ${\mathrm{CuSiO}}_{3}$ the appearance of a small set of magnetic superstructure reflections; the determined antiferromagnetic order can be described by a commensurate propagation vector of $\mathbf{q}=(1/2,0,1/8)$ with respect to the chemical Pbmm unit cell. From the long modulation along the chain a ferromagnetic next neighbor magnetic exchange is deduced, whereas next nearest neighbor coupling is expected to be antiferromagnetic.