Giant magnetisation step in Fe₂: Molecular nanomagnets in the weak exchange limit

¹ 1. Physikalisches Institut, Universität Stuttgart - Pfaffenwaldring 57, 70550 Stuttgart, Germany, EU
² London Centre for Nanotechnology, University College London - 17-19 Gordon Street, London WC1H 0AH, UK, EU
³ CNRS, Université de Bordeaux, ICMCB - avenue du Docteur Schweitzer, 33608 Pessac Cedex, France, EU
⁴ 1. Institut für Theoretische Physik, Universität Stuttgart - Pfaffenwaldring 57, 70550 Stuttgart, Germany, EU
⁵ Grenoble High Magnetic Field Laboratory, CNRS - BP 166, 38042 Grenoble Cedex 9, France, EU
⁶ Institut für Physikalische Chemie, Universität Stuttgart - Pfaffenwaldring 55, 70550 Stuttgart, Germany, EU

^a slageren@ipc.uni-stuttgart.de

Received: 9 May 2011
Accepted: 11 July 2011

Abstract

We investigate a Fe₂ molecular nanomagnet that displays a giant, field-induced step in its magnetisation curve. Detailed magnetisation and magnetic torque investigations demonstrate that in this Fe₂ system the single-ion anisotropy is dominant over the isotropic exchange coupling. Accurate spin Hamiltonian parameter values and tensor orientations are obtained. The theoretical analysis reveals that this system is a very promising candidate for the direct observation of the Néel vector tunnel splitting in weakly coupled molecular nanomagnets.