Magnetic resonances and magnetization in the low-dimensional spin system CsNiCl3

We present magentic resonance and magnetization measurements in the low dimensional spin system CsNiCl3 for temperatures down to 1.5 K and in magnetic fields up to 14 T. The frequency range from 35 GHz to 380 GHz is much larger than for previous experiments. The outstanding features of these experiments are a spreading of the magnetic resonance branches in high fields belowT N and an upturn of the magnetization at higher fields and for temperatures below 20 K. Wheras we can interpret our resonance data with a six sublattice model invoking a large interchain exchange, the magnetization points to typical one dimensional behaviour in higher fields. A theory for a consistent description of resonance data, spinwave spectra and magnetization is required.