Comment on: Quantum interference of tunnel trajectories between states of different spin length in a dimeric molecular nanomagnet

Abstract

Ramsey et al. [Nature Phys. 4, 277-281 (2008)] report the observation of quantum interference associated with tunnelling trajectories between states of different total spin length in a dimeric molecular nanomagnet. They argue that the interference is a consequence of the unique characteristics of a molecular Mn12 wheel, which behaves as a molecular dimer with weak ferromagnetic exchange coupling. We show here that the data published by Ramsey et al. are not consistent and unfortunately mostly wrong. We show further that the Landau-Zener (LZ) formula, which links the tunnel probability with the tunnel splitting, can only be applied in a well-defined experimental region, which lays outside the region accessed by Ramsey and colleagues. Only a lower-limit estimate of the tunnel splitting can be obtained, showing that the observed transition cannot be explained with the dimer model. We also present other shortcomings of the paper questioning the dimer model, and that the alignment of the magnetic field is crucial for observing quantum interference.

This third version contains a reply to arXiv:0806.1922

References in corpus (7)

• Observation of the distribution of molecular spin states by resonant quantum tunneling of the magnetization
• Nonadiabatic Landau Zener tunneling in Fe_8 molecular nanomagnets
• Spin-spin cross-relaxation in single-molecule magnets
• Quantum phase interference (Berry phase) in single-molecule magnets of Mn12
• Landau Zener method to study quantum phase interference of Fe8 molecular nanomagnets
• Landau-Zener tunneling in the presence of weak intermolecular interactions in a crystal of Mn4 single-molecule magnets
• Quantum Step Heights in Hysteresis Loops of Molecular Magnets