Thursday, October 13, 2011, 1:30 pm — Small Seminar Room, Bldg. 510
Strongly correlated oxides have been the subject of intense study for the last two decades. Many of these materials exhibit exciting and technically useful properties; examples include high temperature superconductivity, colossal magnetoresistance, ferromagnetism and ferroelectricity. Layered ruthenates in the Ruddlesden-Popper series (Sr,Ca)n+1RunO3n+1 exhibit exceptionally rich ground state properties, such as unconventional spin-triplet superconductivity, orbital ordering, and metamagnetic quantum criticality. These unusually rich ground states headline the complex interplay between the charge, spin, lattice and orbital degrees of freedom in ruthenates, and provide fantastic opportunities to study novel quantum phenomena tuned by non-thermal parameters like chemical doping, pressure, and magnetic field. In this talk, I give a brief overview of the research in this area and then discuss our progress in the study of these materials. I focus primarily on two materials, the bilayered Ca3Ru2O7 and trilayered Sr4Ru3O10, each with their own exceptionally rich ground states. In Ca3Ru2O7 we have revealed that the magnetic states unusually evolve with in-plane rotation of magnetic field. We probed crossover magnetic states in close proximity to phase boundaries, polarized paramagnetic states at critical angles between the b- and a-axes, and bulk spin valve behavior tuned by in-plane rotation of magnetic field. For Sr4Ru3O10, we have addressed the possible origin of its puzzling coexistence of ferromagnetism and metamagnetism. Our results suggest that the magnetism of this material is orbital dependent: the Ru 4dxy orbital is ferromagnetic, while the dxz,yz orbitals are metamagnetic. Our work shows that such orbital dependent magnetism results in very unusual properties. Finally, I briefly discuss the potential for applications in Mott insulating Ca2RuO4. We have successfully tuned the Mott transition using chemical substitution to make it potentially useful as an uncooled
Hosted by: Igor Zaliznyak
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