Neutron scattering study of the field-induced soliton lattice in CuGeO₃

CuGeO$_3$ undergoes a transition from a spin-Peierls phase to an incommensurate phase at a critical field of $H_c\approx 12.5$ T. In the high-field phase a lattice of solitons forms, with both structural and magnetic components, and these have been studied using neutron scattering techniques. Our results provide direct evidence for a long-ranged magnetic soliton structure which has both staggered and uniform magnetizations, and with amplitudes that are broadly in accord with theoretical estimates. The magnetic soliton width, $\Gamma$, and the field dependence of the incommensurability, $\delta k_{sp}$, are found to agree well with theoretical predictions.