Geometrically Frustrated Magnets as Model Systems
Final rept. 15 Jan 1998-31 Aug 2000
NOTRE DAME UNIV IN
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The specific aim of this research program has been to understand the cooperative magnetic properties of geometrically frustrated antiferromagnets which are model frustrated systems. We have performed extensive thermal studies of one such material, gadolinium gallium garnet, which has highly unusual ground state properties. Because of its purity and the energy scale of the spin-spin interactions, this system offers a unique model to study the consequences of strong geometrical frustration. We have characterized a novel spin state in this material which appears to be a three dimensional spin liquid, and we have shown that it is both distinct from a spin glass and has a highly unusual phase boundary with a long-range-ordered anti ferromagnetic state. These results enhance our understanding of geometrically frustrated systems in that they greatly broaden the range of cooperative behavior which has been observed in such systems. In particular we have made the first study of the thermal excitations in a three dimensional cooperative spin-liquid state. We also have begun studies of two other types of geometrically frustrated systems a pyrochlore lattice of corner sharing tetrahedra and a kagome lattice of corner sharing triangles. In both of these systems we are examining the evolution of frustration as a function of dilution of the frustrated lattice with non-magnetic impurities.
- Electricity and Magnetism