Metamagnetic Quantum Criticality Revealed by 17O-NMR in the Itinerant Metamagnet Sr3Ru2O7

TL;DR

This study uses 17O-NMR to investigate spin dynamics near a metamagnetic quantum critical point in Sr3Ru2O7, revealing non-Fermi liquid behavior and dominant antiferromagnetic fluctuations at the critical field.

Contribution

It provides direct NMR evidence of quantum critical spin dynamics and identifies antiferromagnetic fluctuations as dominant near the metamagnetic critical point in Sr3Ru2O7.

Findings

Enhanced 1/T1T near critical field

Non-Fermi liquid behavior down to 0.3 K

Antiferromagnetic fluctuations dominate at criticality

Abstract

We have investigated the spin dynamics in the bilayered perovskite Sr3Ru2O7 as a function of magnetic field and temperature using 17O-NMR. This system sits close to a metamagnetic quantum critical point (MMQCP) for the field perpendicular to the ruthenium oxide planes. We confirm Fermi-liquid behavior at low temperatures except for a narrow field region close to the MMQCP. The nuclear spin-lattice relaxation rate divided by temperature 1/T1T is enhanced on approaching the metamagnetic critical field of 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 0 K, which is a 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.