Abstract
We identify a class of zero-dimensional classical and quantum Heisenberg spin systems exhibiting anomalous behavior in an external magnetic field similar to that found for the geometrically frustrated kagome lattice of classical spins. Our calculations for the isotropic Heisenberg model show the emergence of a pronounced minimum in the differential susceptibility at as the temperature is raised from 0 K for structures based on corner-sharing triangles, specifically the octahedron, cuboctahedron, and icosidodecahedron. As the first experimental evidence we note that the giant Keplerate magnetic molecule ( ions on the 30 vertices of an icosidodecahedron) exhibits this behavior. For low when two competing families of spin configurations exist of which one behaves magnetically “stiff” leading to a reduction of .
- Received 18 May 2004
DOI:https://doi.org/10.1103/PhysRevLett.94.017205
©2005 American Physical Society