The lowest states of an undoped copper-oxide cluster are determined numerically and fitted by a spin Hamiltonian containing a cyclic 4-spin exchange interaction. The size of this interaction is found to be about a quarter of the size of the nearest-neighbor Heisenberg exchange. The 4-spin exchange leads to a renormalization of spin-wave properties and to extra features in magnetic Raman scattering. The calculated exchange parameters are consistent with the observed spin-wave velocity.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering