Definitive spectroscopic determination of the transverse interactions responsible for the magnetic quantum tunneling in Mn12-acetate

TL;DR

This study uses angle-dependent EPR to identify the transverse anisotropies in Mn12-acetate, revealing intrinsic and disorder-induced contributions that explain magnetic quantum tunneling behaviors.

Contribution

It provides the first detailed spectroscopic evidence distinguishing intrinsic and disorder-related transverse anisotropies in Mn12-acetate.

Findings

Four-fold variation in resonance positions due to intrinsic fourth order anisotropy

Four-fold variation in lineshapes from disorder-induced quadratic anisotropy

Results explain magnetic quantum tunneling phenomena in Mn12-acetate

Abstract

We present detailed angle-dependent single crystal electron paramagnetic resonance (EPR) data for field rotations in the hard plane of the S=10 single molecule magnet Mn12-acetate. A clear four-fold variation in the resonance positions may be attributed to an intrinsic fourth order transverse anisotropy (O44). Meanwhile, a four-fold variation of the EPR lineshapes confirms a recently proposed model wherein disorder associated with the acetic acid of crystallization induces a locally varying quadratic (rhombic) transverse anisotropy (O22). These findings explain most aspects of the magnetic quantum tunneling observed in Mn12-acetate.