From inelastic neutron scattering experiments, we demonstrate quantum tunneling of the Neel vector in the antiferromagnetic molecular ferric wheel CsFe8. Analysis of the linewidth of the tunneling transition evidences coherent tunneling.

The theoretical consideration of mesoscopic quantum coherence (MQC) in small antiferromagnetic (AF) particles a decade ago, and the prediction that it should be more robust than in ferromagnetic particles [1], has stimulated intense efforts in this direction. Subsequent experimental studies on ferritin clusters remained controversial [2, 3]. Several years ago it was suggested that AF molecular wheels, i.e., molecules in which an even number of magnetic metal centers are arranged in a ring, may exhibit MQC as coherent tun