Spin Dynamics of the Half-Integer-Spin Quasi-One-Dimensional Heisenberg Antiferromagnet CsMnI3

Magnetic excitations of CsMnI 3 , a quasi-one-dimensional Heisenberg antiferromagnet with S =5/2, have been measured by means of inelastic neutron scattering. Magnetic excitations in the low temperature phase are in good agreement with the predictions of the conventional linear spin-wave theory. In particular, in accordance with the linear spin-wave theory, we found three separate modes at Q =(0, 0, 1) instead of a threefold degenerate mode as seen in CsNiCl 3 ( S =1). It confirms that the spin dynamics of the integer spin value system are very different from those of the half-integer spin value system, even in their three-dimensionally ordered phase. Magnetic excitations in the intermediat…