Metamagnetism of single crystal Ca3Ru2O7 in high magnetic fields

Ca3Ru2O7, which has a double-layered structure related to perovskites and high-T-c cuprates, exhibits several coupled magnetic and transport phases. As-grown single crystals have nonmetallic conductivity for T < T-M = 48 K, antiferromagnetic ordering up to T-N = 56 K and "bad metal" conductivity, linear in temperature for T > T-N. The current study reveals a metamagnetic transition with an accompanying nonmetal to metal transition found in pulsed high magnetic fields (H-c = 37 T) for the field directed perpendicular to the Ru-O planes in the "hard" axis (001) direction of this highly anisotropic system. By contrast, the transition occurs at 6T for the field along the "easy" axis (110). The resistivity for current along(110) or (001) is anisotropic in zero field at low temperatures but becomes isotropic with H > H-c applied along the easy axis, in contrast to results expected from Fermi-liquid models. (C) 1998 Elsevier Science B.V. All rights reserved.