Evidence for the S=9 excited state in Mn12-bromoacetate measured by electron paramagnetic resonance

TL;DR

This study uses high-frequency EPR to identify an S=9 excited state in Mn12-bromoacetate, revealing insights into its magnetic states and suggesting it as a better candidate for quantum effects research.

Contribution

The paper reports the first identification of an S=9 excited state in Mn12-bromoacetate using high-frequency EPR, highlighting its potential for studying quantum phenomena in high-symmetry S=10 SMMs.

Findings

S=9 manifold located about 40 K above ground state

Mn12-BrAc has similar crystal-field parameters to Mn12-Ac

Absence of disorder-related EPR features in Mn12-BrAc

Abstract

We present high-frequency high-field electron paramagnetic resonance (EPR) measurements on the dodecanuclear manganese complex Mn12-bromoacetate (Mn12-BrAc). The crystal-field parameters are found to be identical to those of the original compound Mn12-acetate (Mn12-Ac). A detailed analysis of the frequency and temperature dependence of anomalous peaks observed in the EPR spectra of Mn12-BrAc enables us to locate the S=9 manifold at about 40 K above the Ms= +/-10 ground state of this nominally S=10 system. This is very close to the Ms = +/-6 state of the S = 10 manifold, thus suggesting pathways for the thermally assisted magnetization dynamics and related properties. Finally, the EPR fine structures recently attributed to disorder associated with the acetic acid of crystallization in Mn12-Ac are absent in the present measurements, thus suggesting that the Mn12-BrAc complex represents a more suitable candidate for measurements of quantum effects in high symmetry S=10 SMMs.