Spin Dynamics in an Ordered Stripe Phase

Abstract

Inelastic neutron scattering has been used to measure the low-energy spin excitations in the ordered charge-stripe phase of ${{\mathrm{La}}_{2}\mathrm{NiO}}_{4+\ensuremath{\delta}}$ with $\ensuremath{\delta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.133$. Spin-wave-like excitations disperse away from the incommensurate magnetic superlattice points with a velocity $\ensuremath{\sim}60%$ of that in the $\ensuremath{\delta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ compound. Incommensurate inelastic peaks remain well resolved up to at least twice the magnetic ordering temperature. Paramagnetic scattering from a $\ensuremath{\delta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.105$ sample, which has a N\'eel-ordered ground state, shows anomalies suggestive of incipient stripe correlations. Similarities between these results and measurements on superconducting cuprates are discussed.