Polarized Neutron Inelastic Scattering Study of the Anisotropic Magnetic Fluctuations in the Quasi-1D Ising-like Antiferromagnet TlCoCl${}_3$

Polarized neutron inelastic scattering experiments have been carried out in the quasi-1D Ising-like antiferromagnet TlCoCl${}_3$. We observed the longitudinal magnetic fluctuation $S_{zz}(Q,\omega )$ for the spin-wave excitation continuum, which has not been observed in the unpolarized neutron inelastic scattering experiments of the quasi-1D Ising-like antiferromagnets CsCoCl${}_3$ and TlCoCl${}_3$ so far, together with the transverse magnetic fluctuation $S_{xx}(Q,\omega )$. We compared both obtained intensities of $S_{xx}(Q,\omega )$ and $S_{zz}(Q,\omega )$ with the perturbation theory from the pure Ising limit by Ishimura and Shiba, and a semi-quantitative agreement was found.