Charge and spin dynamics of an ordered stripe phase in La_{1 2/3}Sr_1/3NiO₄ by Raman spectroscopy

For La_{1 2/3}Sr_1/3NiO₄ - a commensurately doped Mott-Hubbard system - charge- and spin-ordering in a stripe phase have been investigated by phononic and magnetic Raman scattering. Formation of a superlattice and an opening of a pseudo-gap 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.