Transport and thermodynamic properties of Sr₃Ru ₂O₇ near the quantum critical point

The specific heat and electrical resistivity of Sr₃Ru ₂O₇ single crystals are measured in several magnetic fields applied along the c axis for temperatures below 2 K and at fields up to 17 T. Near the critical metamagnetic field at B₁* ∼ 7.8 T, the electronic specific heat divided by temperature increases logarithmically as the temperature decreases, over a large range of T, before saturating below a certain T* (which is sample dependent), indicating a crossover from a non-Fermi liquid (NFL) region dominated by quantum critical fluctuations to a Fermi liquid (FL) region. This crossover from a NFL to a FL state is also observed in the resistivity data near the critical metamagnetic field for I||c and B||c. The coefficient of electronic specific heat, γ, plotted as a function of field shows two peaks, consistent with the two metamagnetic transitions observed in magnetization and magnetic torque measurements. At the lowest temperatures, a Schottky-like upturn with decreasing temperature is observed. The coefficient of the Schottky anomaly exhibits a field dependence similar to that of γ, implying an influence by the electrons near the Fermi surface on the Schottky level splitting.