Fig. 1: Main magnetic concepts employed in this study.
Slow relaxation of the magnetisation in SIMs can manifest in different ways. a Spin blocking is often characterised by a temperature- and frequency-dependent out-of-phase ac susceptibility χ”, being TB3H the temperature for the maximum χ” at 103 Hz in the presence of a magnetic field. b These relaxation dynamics have most often been modelled as an Orbach process (black dots), using the Arrhenius equation. Raman (green dots) and quantum tunnelling (red dots) processes can also be relevant. c Magnetic hysteresis can be full (orange) or “pinched”, also known as butterfly (purple), where the latter signals a fast relaxation at zero magnetic field. d Scheme of different relaxation processes: tunnelling involves just the states within the ground doublet, Orbach process takes place via an excited state, and Raman process happens via a virtual state.
