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Condensed Matter Seminars

ics Condensed Matter
Thursday, January 31, 2008
4:00 PM
Physics Building, Room 204
Note special time.
Note special room.
Bruce Gaulin [Host: Seung-Hun Lee]
McMaster University
"Frustrated and Satisfied Ground States in Pyrochlore Magnets"
 Slideshow (PDF)
Geometrical frustration arises quite generally when pairwise interactions in magnetic materials are incompatable with their local geometry. This often involves magnetic materials made up of assemblies of triangles or tetrahedra. The frustration is manifest by disordered low temperature states for the magnetic material - some of which are described by spin liquids, spin glasses, and spin ice. I will discuss (mostly) neutron scattering work using DCS at NIST on two magnetic pyrochlores Tb2Ti2O7 and Ho2Ti2O7, which can be thought of as Ising-like moments decorating a network of corner-sharing tetrahedra. Tb2Ti2O7 displays a spin liquid, or cooperative paramagnetic ground state, but can be brought to order in an applied magnetic field. Ho2Ti2O7 displays a static disordered "spin ice" state at low temperatures.

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