For ${\mathrm{La}}_{1\frac{2}{3}}{\mathrm{Sr}}_{\frac{1}{3}}{\mathrm{NiO}}_4$, a commensurately doped Mott-Hubbard system, charge and spin ordering in a stripe phase has been investigated by phonon and magnetic Raman scattering. Formation of a superlattice and an opening of a pseudogap in the electron-hole excitation spectra as well as two types of double-spin excitations—within the antiferromagnetic domain and across the domain wall—are observed below the charge ordering transition. The temperature dependence suggests that the spin ordering is driven by charge ordering and that fluctuating stripes persist above the ordering transition.

• Received 8 July 1997

DOI:https://doi.org/10.1103/PhysRevLett.80.564