55Mn nuclear spin relaxation in the truly axial single-molecule magnet Mn12-t-butylacetate thermally-activated down to 400 mK

We report on the measurements of the spin–lattice relaxation time, T1, of Mn12O12(O2CCH2But)16(CH3OH)4 · CH3OH, a truly axial symmetry Mn12 single-molecule magnet (SMM), with the view to examining the role of point symmetry and lattice-solvate molecules in this Mn12 SMM. The measurements were made over 0.390–1.8 K, on freshly prepared single crystals which afforded much higher spectral resolution than magnetically aligned powder. The measured T1 is found to be thermally activated, and follows either a T2 or exponential behavior over 0.390–0.7 K, in contrast to the temperature-independent behavior for Mn12-acetate, where Jahn–Teller isomers are thought to be the origin of the temperature-independent nuclear relaxation mechanism.

Graphical abstractInverse T1 of the Mn(1) peak of Mn12-t-Bu single crystal. Below 0.8 K, temperature-independent behavior is not present, suggesting that quantum tunneling of the magnetization is not responsible for the relaxation of the nuclei in this temperature range.Figure optionsDownload full-size imageDownload as PowerPoint slide