Sub-Kelvin hysteresis of the dilanthanide single-molecule magnet Tb2ScN@C80

Abstract

Magnetic hysteresis is a direct manifestation of non-equilibrium physics that has to be understood if a system shall be used for information storage and processing. The dilanthanide endofullerene Tb2ScN@C80 is shown to be a single-molecule magnet with a remanence time in the order of 100 s at 400 mK. Three different temperature dependent relaxation barriers are discerned. The lowest 1 K barrier is assigned to intermolecular interaction. The 10 K barrier to intramolecular exchange and dipolar coupling and the 50 K barrier to molecular vibrations as it was observed for Dy2ScN@C80. The four orders of magnitude difference in the prefactor between the Tb and the Dy compound in the decay process across the 10 K barrier is assigned to the electron number in the 4f shells that evidences lack of Kramers protection in Tb3+. The sub-Kelvin hysteresis follows changes in the magnetisation at adiabatic and non-adiabatic level crossings of the four possible Tb2 ground state configurations as is inferred from a zero temperature hysteresis model.