Single-molecule magnetostrictor: an {Fe8Gd8} cubic crystal exhibits temperature-dependent magnetostriction

Abstract Molecular magnets, as important category of nanosized magnetic materials have attracted considerable interest for their wide applications such as contrasting agents for magnetic resonance imaging, low-temperature magnetic refrigerants and spintronic devices. Up to date, though magnet-type behaviour has been enhanced to 100 K for single-molecule magnets, the investigation of molecule-originated magnetostriction is still in its infancy. Here we report the observation of a large MS effect (50 ppm at 2 K under a field of 7 T) in a crystal solid of the wheel-like {Fe8Gd8} coordination molecules. The {Fe8Gd8} molecules crystallized in a highly symmetric cubic space group of $Pn\bar{3}n$ and has no long-range magnetic ordering down to 0.2 K. Therefore, we are convinced that such a giant magnetostrictive effect for {Fe8Gd8} is a single-molecule origin. We further used quantum Monte Carlo simulation to fit the temperature-dependent magnetostriction data and gave an excellent overlap with JFe–Gd = 4.81(5) K. Such a strong ferromagnetic interaction between Fe3+ and Gd3+ ensures a large magnetic momentum for {Fe8Gd8}, which is the key source of magnetoelastic response to the external field at low temperatures. Therefore, this work explicitly demonstrates that predominantly intramolecular exchange-coupling can cause magnetostriction, inspiring the design of new magnetostrictive materials.