Metamagnetic Transition and Low-Energy Spin Density Fluctuations in Sr₃Ru₂O₇

The magnetic properties of the bilayer ruthenate Sr3Ru2O7 as investigated by neutron scattering are reviewed. No long range magnetic order is observed down to 40 mK, but instead a metamagnetic transition which is induced by a moderate magnetic field at low temperatures. In zero field, the spectrum of the spin fluctuations reveals that at low temperature the magnetic correlations in this material are antiferromagnetic in nature. The wavevectors at which the signal is strongest are incommensurate and appear to be determined by Fermi surface nesting. The low energy scale of the fluctuations suggests that they are intimately related to the metamagnetic transition.