Quantum Phase Interference and Neel-Vector Tunneling in Antiferromagnetic Molecular Wheels

The antiferromagnetic molecular wheel Fe-18 of 18 exchange-coupled Fe-III ions has been studied by magnetic torque, magnetization, and inelastic neutron scattering. The combined data show that the low-temperature magnetism of Fe-18 is very accurately described by the Neel-vector tunneling (NVT) scenario, as unfolded by semiclassical theory. In addition, the magnetic torque as a function of applied field exhibits oscillations that reflect the oscillations in the NVT splitting with field due to quantum phase interference.