Raman Scattering of the Charge-Spin Stripes inLa1.67Sr0.33NiO4

Raman scattering spectra have been investigated for a single crystal of ${\mathrm{La}}_{1.67}{\mathrm{Sr}}_{0.33}{\mathrm{NiO}}_4$ which shows stripe ordering of charge ( $T_{\mathrm{c}}=230\mathrm{}\mathrm{K}$) and spin ( $T_{\mathrm{s}}=180\mathrm{}\mathrm{K}$). Upon the charge ordering, the activated phonon peaks grow with the evolution of the charge modulation amplitude, while the electronic Raman continuum of the metallic state abruptly disappears. The two broad peaks with the $B_{1g}$ symmetry arising from the two-magnon excitations emerge immediately below $T_{\mathrm{c}}$, indicating the evolution of the two-dimensional antiferromagnetic spin correlation in the charge-ordered state even above $T_{\mathrm{s}}$.