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Competing Spin Phases in Geometrically Frustrated Magnetic Molecules

C. Schroeder·H. Nojiri·J. Schnack·P. Hage·M. Luban·P. Koegerler
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Abstract

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.

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C. Schroeder, H. Nojiri, J. Schnack, P. Hage, M. Luban, P. Koegerler. 2004-12-13. Competing Spin Phases in Geometrically Frustrated Magnetic Molecules. https://doi.org/10.1103/physrevlett.94.017205

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