Competing Spin Phases in Geometrically Frustrated Magnetic Molecules

TL;DR

This paper investigates zero-dimensional geometrically frustrated Heisenberg spin systems, revealing a susceptibility minimum at B_sat/3 due to competing spin configurations, supported by theoretical calculations and experimental magnetization data.

Contribution

It introduces a new understanding of magnetic behavior in frustrated molecules, highlighting the emergence of a susceptibility minimum at B_sat/3 in specific spin structures.

Findings

Susceptibility minimum at B_sat/3 in certain frustrated molecules

Agreement between theoretical models and experimental magnetization data

Identification of competing spin configurations affecting magnetic response

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.