  The magnon disp ersion in Ca2RuO4 has been determined by inelastic neutron
scattering on single crytals containing 1% of Ti. The dispersion is well
described by a conventional Heisenberg model suggesting a local moment model
with nearest neighbor interaction of J=8 meV. Nearest and next-nearest neighbor
interaction as well as inter-layer coupling parameters are required to properly
describe the entire dispersion. Spin-orbit coupling induces a very large
anisotropy gap in the magnetic excitations in apparent contrast with a simple
planar magnetic model. Orbital ordering breaking tetragonal symmetry, and
strong spin-orbit coupling can thus be identified as important factors in this
system.
