Raman-scattering study of the charge and spin dynamics of the layered ruthenium oxide Ca3Ru2O7

We report a Raman-scattering study of the relationship among the charge, spin, and lattice dynamics of Ca3Ru2O7. The metal-insulator (MI) transition (T-MI similar to 48 K) in this compound manifests itself as a rapid suppression of low-frequency electronic scattering intensity, reflecting the opening of a charge gap, Delta(c) similar to 760 cm(-1), and a concomitant softening and broadening of the 438 cm(-1) out-of-phase oxygen phonon mode. Furthermore, the transition to antiferromagnetic order below T-N similar to 56 K is associated with the development of a B-1g resonance peak near 58 cm(-1). We identify this feature as a two-magnon process, based upon which we estimate an in-plane antiferromagnetic exchange coupling of J(parallel to) similar to 8.7 cm(-1) in Ca3Ru2O7. [S0163-1829(99)51334-9].