A high-frequency EPR study of a new S = 10 Mn12 single-molecule magnet

We will present a detailed angle-resolved high-frequency EPR study of a recently discovered analog of the Mn$_{12}${\-}acetate single-molecule magnet (SMM). Like the acetate, the new complex [Mn$_{12}$O$_{12}$(O$_{2}$CCH$_{2}$Bu$^{t})_{16}$(CH$_{3}$OH)$_{4}$]$\cdot $CH$_{3}$OH (Mn$_{12}${\-}tBuAc), possesses a spin $S$~=~10 ground state and $S_{4}$ site symmetry. Magnetic measurements also reveal the usual resonant magnetization tunneling steps in the low temperature hysteresis loops. However, we show that the solvent-disorder-induced anomalies reported in the EPR spectra for Mn$_{12}$-acetate$^{1}$ are absent for Mn$_{12}${\-}tBuAc. This suggests that Mn$_{12}$-tBuAc is intrinsically cleaner, and that detailed studies of this compound may reveal important new information concerning the quantum dynamics of large spins. Indeed, our analysis of the EPR line widths suggest that they are close to the intrinsic lifetime broadened limit, which may make it possible to extract information concerning electronic relaxation times (T$_{1}$ and T$_{2})$. $^{1}$S. Takahashi et al., Phys. Rev. B \textbf{70}, 094429 (2004)