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

Molecular magnets, as an 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 (MS) 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 [Formula: see text] and have 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 J _Fe-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.