Characterisation of magnetic relaxation on extremely long timescales*

Recent advances in the field of single-molecule magnets have led to the development of very slow relaxing species. However, challenges remain in understanding the effect local environment has on the quantum tunnelling of magnetisation (QTM) and Raman processes in these materials. This is partly due to the extremely long relaxation times τ that are now being observed. For τ of the order of a week or longer, it is not feasible to measure DC decays all the way to equilibrium (M_eq). Whilst we can calculate M_eq, one cannot model how M(H) approaches M_eq. This leads to an increasingly large asymmetry and width of the distribution of the rate, such that the measured τ* becomes meaningless. We investigate the distribution of the stretched exponential used to model DC decay measurements to develop a more realistic measure of τ. We also present low-temperature magnetometry measurements of the high-performance SMM [Dy(Cp^ttt)₂][BArF] [1] secured in eicosane, and dissolved in dichloromethane and difluorobenzene. Using this, we explore the effect solvating samples has on the relaxation processes.

[1]C.Goodwin et al., Nat. 548, 439 (2019)