Europhys. Lett.
Volume 63, Number 5, September 2003
Page(s) 764 - 770
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 November 2003
DOI: 10.1209/epl/i2003-00574-3
Europhys. Lett., 63 (5) , pp. 764-770 (2003)

Energy spectrum of the $\chem{Fe_4}$ molecular magnet

T. J. Burns and J. Oitmaa

School of Physics, The University of New South Wales - Sydney, NSW 2052, Australia

(Received 24 January 2003; accepted in final form 17 June 2003)

We present a theoretical analysis of the magnetic energy level spectrum of the molecular complex $\chem{Fe_4(OCH_3)}$ (dpm)6, which is an example of a "molecular magnet". Using a Heisenberg exchange model, we investigate the energy spectrum and the deviations which result from the slight asymmetry of the cluster. We derive an analytical expression for the crystal field splitting of the ground state as a function of the anisotropy. Finally, we establish the existence of diabolical points in the magnetic-field spectrum and compare to predictions made by semiclassical and perturbation theory approaches, and investigate how the location of these points is affected by higher-order anisotropy terms.

75.50.Xx - Molecular magnets.
75.10.Dg - Crystal-field theory and spin Hamiltonians.

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