Persistence of Ising-like easy-axis spin correlations in the paramagnetic state of the spin-1 chain compound NiTe2O5

Abstract

A Te-125 nuclear magnetic resonance (NMR) study was carried out in the paramagnetic state of the recently discovered quasi-one-dimensional spin-1 chain compound NiTe2O5. We observed that the Te-125 NMR spectrum splits into two in a magnetic field applied along the c axis. Based on the strong temperature variation of the rela-tive intensity ratio of the split lines, we infer that the line splitting arises from the two sublattice susceptibilities induced in opposite directions along the chains. In great support of this interpretation, a quantitative analysis of the spin-lattice relaxation rate T-1(-1) and the Knight shift data unravels dominant transverse spin fluctuations. We conclude that Ising-like uniaxial spin correlations persist up to surprisingly high temperatures compared to the exchange energy scales. Spin-charge coupling mechanism via a self-doping effect may be important.