Quantum oscillations, colossal magnetoresistance, and the magnetoelastic interaction in bilayered Ca3Ru2O7 -: art. no. 184405

We report magnetic and interplane transport properties of Ca3Ru2O7 at high magnetic fields and low temperatures. Ca3Ru2O7 with a bilayered orthorhombic structure is a Mott-like system with a narrow charge gap of 0.1 eV. Of a host of unusual physical phenomena revealed in this study, a few are particularly intriguing: (1) a collapse of the c-axis lattice parameter at a metal-nonmetal transition, T-MI(=48 K), and a rapid increase of T-MI with low uniaxial pressure applied along the c axis; (2) quantum oscillations in the gapped, nonmetallic state for 20 mK<T<6.5 K; (3) tunneling colossal magnetoresistance, which yields a precipitate drop in resistivity by as much as 3 orders of magnitude; (4) different in-plane anisotropies of the colossal magnetoresistance and magnetization. All results appear to indicate a highly anisotropic ground state and a critical role of coupling between lattice and magnetism. The implication of these phenomena is discussed.