Geometric-phase interference in a Mn_{12} single-molecule magnet with four-fold rotational symmetry

TL;DR

This study demonstrates geometric-phase interference effects in a four-fold symmetric single-molecule magnet, revealing how transverse magnetic fields influence quantum tunneling rates and confirming theoretical predictions through detailed numerical modeling.

Contribution

First experimental evidence of geometric-phase interference in a four-fold symmetric single-molecule magnet, supported by numerical calculations matching observed behavior.

Findings

Magnetic relaxation rate increases abruptly at specific transverse fields.

Interference effects are suppressed when rotating the field away from the hard axis.

Numerical models accurately reproduce the experimental data.

Abstract

We study the magnetic relaxation rate Gamma of the single-molecule magnet Mn_{12}-tBuAc as a function of magnetic field component H_T transverse to the molecule's easy axis. When the spin is near a magnetic quantum tunneling resonance, we find that Gamma increases abruptly at certain values of H_T. These increases are observed just beyond values of H_T at which a geometric-phase interference effect suppresses tunneling between two excited energy levels. The effect is washed out by rotating H_T away from the spin's hard axis, thereby suppressing the interference effect. Detailed numerical calculations of Gamma using the known spin Hamiltonian accurately reproduce the observed behavior. These results are the first experimental evidence for geometric-phase interference in a single-molecule magnet with true four-fold symmetry.