Michel Gingras, Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, Canada
Magnetic materials have long offered physicists the opportunity to study some of the general principles that govern collective phenomena in Nature. For example, different materials possess different effective spin symmetry, allowing experimentalists and theorists to explore the role of combined spin symmetry and spatial dimensionality on the spontaneous development, or not, of long-range order. Because of the wide variety of interesting and complex behaviors that they display, highly frustrated magnetic pyrochlore oxides have attracted much interest for over thirty years. Since the mid 1990s, significant progress has been made in understanding pyrochlore oxides with magnetic moments having one spin components, or Ising systems. This is the case of the popular 'spin ices'. More recently, combined experimental and theoretical efforts have been directed at understanding pyrochlores described by two component spins (XY systems) and three component spins (Heisenberg systems). These two classes appear as rich as the Ising spin ices, displaying intriguing phenomena such as spin liquid behavior, order-by-disorder and persistent spin dynamics down to very low-temperature. In this seminar, I will present an overview of the current understanding of some of the most interesting non-Ising pyrochlores that has emerged over past couple of years.
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