Abstract
Here we report a study of the spin dynamics in the ferromagnetic chain compound Li2CuO2. Inelastic neutron scattering measurements allow for the spin Hamiltonian to be determined using a J1−J2 XXZ-Heisenberg spin chain model with weak interchain interactions. The primary exchange parameters determined from our data are qualitatively consistent with those of Lorenz et al. [Europhys. Lett. 88, 37002 (2009)], and our data allow for the resolution of additional interchain exchange interactions. We also observe the formation of two- and, potentially, three-magnon bound states. The two-magnon bound state exists only in the magnetically ordered phase of this material, consistent with stabilization by the weak, Ising-like exchange anisotropy of the nearest-neighbor intrachain interaction. In contrast, the potential three-magnon state persists in a finite temperature regime above TN, indicating an unconventional character. Our results establish Li2CuO2 as an experimental platform for the study of exchange anisotropy-stabilized bound states in a ferromagnetic chain.
