Temperature evolution of the magnetic excitations in charge ordered La5/3Sr1/3NiO4

Polarized- and unpolarized-neutron scattering was used to study the temperature evolution of the magnetic excitations of charge ordered La5/3Sr1/3NiO4. We studied two features in detail: (i) the resonance-like scattering at 27 meV in the quasi-two-dimensional magnetic excitations from the ordered Ni2+ (S = 1) spins, and (ii) the diffuse scattering associated with quasi-one-dimensional antiferromagnetic correlations along the stripes. Although both these features persist up to at least ~125 K, their temperature dependences are found to be quite different. We argue from the results that the resonance-like feature observed in La2-xSrxNiO4 (x~1/3) is not caused by a coupling between the spin dynamics of the two magnetic sub-systems.