Abstract
NMR frequency shifts K and spin-lattice relaxation rates 1/ have been measured in the chain nickelate . Between 40 and 300 K the anisotropic shift is proportional to the isotropic shift , which is incompatible with existing theory of the spin susceptibility in Haldane-gap antiferromagnets. In addition, different energy gaps are obtained from shift and spin-lattice relaxation data: ()=80±5 K, whereas (1/)=122±8 K. This is also unexpected, and indicates that the dynamic susceptibility χ(q,ω) is more strongly gapped for large q than for q=0.
- Received 10 August 1995
DOI:https://doi.org/10.1103/PhysRevB.52.R9835
©1995 American Physical Society