Abstract
Neutron elastic and inelastic scattering measurements have been performed in order to investigate the spin structure and the magnetic excitations in the impurity-induced antiferromagnetic ordered phase of the doped spin gap system with The magnetic Bragg reflections indicative of the ordering were observed at with integer h and odd l below It was found that the spin structure of the impurity-induced antiferromagnetic ordered phase on average in with is the same as that of the field-induced magnetic ordered phase for in the parent compound The triplet magnetic excitation was clearly observed in the plane and the dispersion relations of the triplet excitation were determined along four different directions. The lowest triplet excitation corresponding to the spin gap was observed at with integer h and odd l, as observed in It was also found that the spin gap increases steeply below upon decreasing temperature. This strongly indicates that the impurity-induced antiferromagnetic ordering coexists with the spin gap state in with
- Received 31 July 2002
DOI:https://doi.org/10.1103/PhysRevB.67.184424
©2003 American Physical Society