Magnesium Oxide Boosts the Hysteresis of Single-Molecule Magnets

A consortium of researchers from PSI and from EPFL has demonstrated that the magnetization lifetimes of TbPc₂ single-molecule magnets is significantly influenced by the employed substrate on which the molecules are deposited. The molecular magnets adsorbed on magnesium oxide grown on a silver substrate exhibit record-wide magnetic hysteresis and record-large remanence. In contrast, when the molecules are deposited directly on the silver substrate, the magnetic hysteresis is barely visible. On both surfaces, the molecules are self-assembled into square-shaped islands with a strong easy-axis magnetic anisotropy perpendicular to the surface plane.

The published data have been obtained using X-ray magnetic circular dichroism at low temperatures down to 3 Kelvin and high magnetic fields up to 7 Tesla, which is able to determine the element-specific magnetic moments of the submonolayer of molecules present at the surface. Furthermore, scanning tunneling microscopy reveals the exact topography of the molecular assembly.

The results open up a path toward molecular magnetic tunneling devices within the framework of molecular spintronics, which exploits the peculiar properties of molecular magnets to perform information processing and storage tasks.