We have found a class of zero-dimensional geometrically frustrated Heisenberg spin systems exhibiting anomalous behavior in an external magnetic field B similar to that occuring in geometrically frustrated planar antiferromagnetic lattices. Our calculations for both the classical and quantum isotropic Heisenberg models show the emergence of a pronounced minimum in the differential susceptibility dM/dB at B_sat/3 as the temperature T is raised from 0K for structures based on corner-sharing triangles, specifically the octahedron, cuboctahedron, and icosidodecahedron. Low temperature measurements of magnetization M versus B for the giant Keplerate magnetic molecule Mo72Fe30 (Fe(3+) ions with spin s=5/2 on the 30 vertices of an icosidodecahedron) are consistent with our calculational results. The minimum in dM/dB is due to the fact that for low temperatures when B is approx. B_sat/3 there exist two competing families of spin configurations of which one behaves magnetically 'stiff' leading to a reduction of the susceptibility.
@article{arxiv.cond-mat/0405405,
title = {Competing Spin Phases in Geometrically Frustrated Magnetic Molecules},
author = {C. Schroeder and H. Nojiri and J. Schnack and P. Hage and M. Luban and P. Koegerler},
journal= {arXiv preprint arXiv:cond-mat/0405405},
year = {2009}
}
Comments
4 pages, 5 figures, to be published in Phys. Rev. Lett