High Frequency electron paramagnetic resonance has been used to observe the magnetic dipole, Δ Ms = ± 1, transitions in the S=9 excited state of the single molecule magnet Fe8Br8. A Boltzmann analysis of the measured intensities locates it at 24 ± 2 K above the S=10 ground state, while the line positions yield its magnetic parameters D = -0.27 K, E = ±0.05 K, and B40 = -1.3× 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 Fe8Br8.
@article{arxiv.cond-mat/0309159,
title = {Characterization of the S = 9 excited state in Fe8Br8 by Electron Paramagnetic Resonance},
author = {D. Zipse and J. M. North and N. S. Dalal and S. Hill and R. S. Edwards},
journal= {arXiv preprint arXiv:cond-mat/0309159},
year = {2009}
}