Kitagawa K, Ishida K, Perry R S, Tayama T, Sakakibara T, Maeno Y
Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
Phys Rev Lett. 2005 Sep 16;95(12):127001. doi: 10.1103/PhysRevLett.95.127001. Epub 2005 Sep 13.
We have investigated the spin dynamics using 17O-NMR in the bilayered perovskite Sr3Ru2O7, which sits close to a metamagnetic quantum critical point. The nuclear spin-lattice relaxation rate divided by temperature 1/T1T is enhanced on approaching the metamagnetic critical field of approximately 7.9 T, and at the critical field 1/T1T continues to increase and does not show Fermi-liquid behavior down to 0.3 K. The temperature dependence of T1T in this region suggests the critical temperature Theta to be approximately 0 K, which is strong evidence that the spin dynamics possesses a quantum critical character. Comparison between uniform susceptibility and 1/T1T 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.
我们利用17O核磁共振研究了双层钙钛矿Sr3Ru2O7中的自旋动力学，该材料接近一个变磁性量子临界点。在接近约7.9 T的变磁性临界场时，核自旋-晶格弛豫率除以温度1/T1T增大，并且在临界场处1/T1T继续增加，直至0.3 K都未表现出费米液体行为。该区域中T1T的温度依赖性表明临界温度θ约为0 K，这有力地证明了自旋动力学具有量子临界特性。均匀磁化率与1/T1T的比较表明，在临界场处反铁磁涨落而非二维铁磁涨落主导了自旋涨落谱，这对于巡游变磁性来说是出乎意料的。
