The ground state of Sr3Ru2O7 revisited; Fermi liquid close to a ferromagnetic instability

Abstract

We show that single-crystalline Sr3Ru2O7 grown by a floating-zone technique is an isotropic paramagnet and a quasi-two dimensional metal as spin-triplet superconducting Sr2RuO4 is. The ground state is Fermi liquid with very low residual resistivity (3 micro ohm cm for in-plane currents) and a nearly ferromagnetic metal with the largest Wilson ratio Rw>10 among paramagnets so far. This contrasts with the ferromagnetic order at Tc=104 K reported on single crystals grown by a flux method [Cao et al., Phys. Rev. B 55, R672 (1997)]. We have also found a dramatic changeover from paramagnetism to ferromagnetism under applied pressure. This suggests the existence of a substantial ferromagnetic instability on the verge of a quantum phase transition in the Fermi liquid state.