Charge and spin dynamics of an ordered stripe phase in La-1 2/3Sr1/3NiO4 by Raman spectroscopy

For La-1 2/3Sr1/3NiO4-a commensurately doped Mott-Hubbard system-charge- an d spin-ordering in a stripe phase have been investigated by phononic and ma gnetic Raman scattering. Formation of a superlattice and an opening of a ps eudo-gap in the electron-hole excitation spectra, as well as two types of d ouble-spin excitations (within the antiferromagnetic domain and across the domain wall) are observed below the charge-ordering transition. The tempera ture dependence suggests that the spin ordering is driven by charge orderin g and that fluctuating stripes persist above the ordering transition. (C) 1 998 Elsevier Science Ltd. All rights reserved.