The ruthenium-based perovskites exhibit a wide variety of interesting collective phenomena related to magnetism originating from the Ru $4d$ electrons. Much remains unknown concerning the nature of magnetic fluctuations and excitations in these systems. We present results of detailed inelastic neutron scattering measurements of ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$ as a function of temperature, probing the ferromagnetic fluctuations of the bilayer structure. A magnetic response is clearly visible for a range of temperatures, $T=3.8\mathrm{K}$ up to $T=100\mathrm{K}$, and for energy transfers between $\hslash \omega =2$ and $14\mathrm{meV}$. These measurements indicate that the ferromagnetic fluctuations manifest in the bilayer structure factor persist to surprisingly large temperatures. This behavior may be related to the proximity of the system in zero magnetic field to the metamagnetic/ferromagnetic transition.

• Received 6 January 2006

DOI:https://doi.org/10.1103/PhysRevB.73.174426