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 me tal'' conductivity, linear in temperature for T > T-N. The current stu dy 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'' a xis (001) direction of this highly anisotropic system. By contrast, th e transition occurs at 6T for the field along the ''easy'' axis (110). The resistivity for current along(110) or (001) is anisotropic in zer o field at low temperatures but becomes isotropic with H > H-c applied along the easy axis, in contrast to results expected from Fermi-liqui d models. (C) 1998 Elsevier Science B.V. All rights reserved.