  Low energy spin excitations were investigated in the static stripe phase of
La_{2-x}Sr_xCuO_4 using elastic and inelastic neutron scattering on single
crystals. For x = 1/8 in which long-range static stripe order exists, an energy
gap of E_g = 4 meV exists in the excitation spectrum in addition to strong
quasi-elastic, incommensurate spin fluctuations associated with the static
stripes. When x increases, the spectral weight of the spin fluctuations shifts
from the quasi-elastic continuum to the excitation spectrum above E_g. The
dynamic correlation length as a function of energy and the temperature
evolution of the energy spectrum suggest a phase separation of two distinct
magnetic phases in real space.
