  The elementary excitations from the conventional magnetic ordered states,
such as ferromagnets and antiferromagnets, are magnons. Here, we elaborate a
case where the well-defined magnons are absent completely and the spin
excitation spectra exhibit an entire continuum in the itinerant edge
ferromagnetic state of graphene arising from the flatband edge electronic
states. Based on the further studies of the entanglement entropy and
finite-size analysis, we show that the continuum other than the Stoner part
results from the spin-1/2 spinons deconfined from magnons. The spinon continuum
in a magnetically ordered state is ascribed to a ferromagnetic Luttinger liquid
in this edge ferromagnet. The investigation is carried out by using the
numerical exact diagonalization method with a projection of the interacting
Hamiltonian onto the flat band.
