Metamagnetic Quantum Criticality Revealed byO17−NMRin the Itinerant MetamagnetSr3Ru2O7

We have investigated the spin dynamics using ${}^{17}\mathrm{O}\mathrm{\text{−}}\mathrm{NMR}$ in the bilayered perovskite ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$, which sits close to a metamagnetic quantum critical point. The nuclear spin-lattice relaxation rate divided by temperature $1/T_{1}T$ is enhanced on approaching the metamagnetic critical field of $\sim 7.9\mathrm{T}$, and at the critical field $1/T_{1}T$ continues to increase and does not show Fermi-liquid behavior down to 0.3 K. The temperature dependence of $T_{1}T$ in this region suggests the critical temperature $\Theta$ to be $\sim 0\mathrm{K}$, which is strong evidence that the spin dynamics possesses a quantum critical character. Comparison between uniform susceptibility and $1/T_{1}T$ reveals that antiferromagnetic fluctuations instead of two-dimensional ferromagnetic fluctuations dominate the spin fluctuation spectrum at the critical field, which is unexpected for itinerant metamagnetism.