Single-molecule magnets: Gadolinium keeps its cool

by Anne Pichon

A cluster formed by calixarenes coordinated to a mixed metal manganese–gadolinium magnetic core has excited states that are populated at low temperature, and shows promise for magnetic refrigeration systems.

Single-molecule magnets (SMMs), which combine properties explained by classical and quantum physics, are attractive not just for fundamental studies, but also for various applications. They are used, for example, in magnetic refrigeration, which relies on materials that alter their temperature under a changing magnetic field — the so-called magnetocaloric effect. SMMs have been built by encapsulating metal clusters within large rigid shells, such as calixarenes.

The magnetism of the cluster was highly isotropic, and exhibited excited spin states that were populated even at low temperature. This resulted in a large magnetocaloric effect and these states only became depopulated under a high external magnetic field. This high ferromagnetic limit, together with the low-lying excited states and the high isotropy, makes this 3d/4f cluster a good candidate to be a low-temperature magnetic refrigerant.

Link to the journal site.