Eur. Phys. J. B 27, 487-495 (2002)
https://doi.org/10.1140/epjb/e2002-00182-1

Spin dynamics and coherent tunnelling in the molecular magnetic rings Fe₆ and Fe₈

¹ Institut für Theoretische Physik, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
² Departement für Physik und Astronomie, Universität Basel, 4056 Basel, Switzerland
³ Theoretische Physik III, Elektronische Korrelationen und Magnetismus, Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany

Corresponding author: ^a bruce.normand@physik.uni-augsburg.de

Received: 22 February 2002
Published online: 25 June 2002

Abstract

We present detailed calculations of low-energy spin dynamics in the “ferric wheel” systems Na:Fe₆ and Cs:Fe₈ in a magnetic field. We compute by exact diagonalisation the low-energy spectra and matrix elements for total-spin and Néel-vector components, and thus the time-dependent correlation functions of these operators. Comparison of our results with the semiclassical theory of coherent quantum tunnelling of the Néel vector demonstrates the validity of a two-state description for the low-energy dynamics of ferric wheels. We discuss the implications of our results for mesoscopic quantum coherent phenomena, and for the experimental techniques to observe them, in molecular magnetic rings.