Characterization of the S = 9 excited state in Fe8Br8 by Electron Paramagnetic Resonance

TL;DR

This study uses high-frequency electron paramagnetic resonance to characterize the excited S=9 state in Fe8Br8, revealing its energy, magnetic parameters, and anisotropy barrier, aiding electronic structure understanding.

Contribution

It provides detailed magnetic parameters and energy positioning of the S=9 state in Fe8Br8, improving understanding of its electronic structure and exchange interactions.

Findings

S=9 state is 24 K above ground state

Magnetic parameters D, E, B4^0 are quantified

Anisotropy barrier for S=9 is 22 K

Abstract

High Frequency electron paramagnetic resonance has been used to observe the magnetic dipole, $\Delta$ M$_s$ = $\pm$ 1, transitions in the $S = 9$ excited state of the single molecule magnet Fe$_8$Br$_8$. A Boltzmann analysis of the measured intensities locates it at 24 $\pm$ 2 K above the $S = 10$ ground state, while the line positions yield its magnetic parameters D = -0.27 K, E = $\pm$0.05 K, and B$_4^0$ = -1.3$\times$ 10$^{-6}$ K. D is thus smaller by 8% and E larger by 7% than for $S = 10$. The anisotropy barrier for $S = 9$ is estimated as 22 K,which is 25% smaller than that for $S = 10$ (29 K). These data also help assign the spin exchange constants(J's) and thus provide a basis for improved electronic structure calculations of Fe$_8$Br$_8$.