Magnetic fingerprint of individual Fe ₄ molecular magnets under compression by a scanning tunnelling microscope

Abstract

Single-molecule magnets (SMMs) present a promising avenue to develop spintronic technologies. Addressing individual molecules with electrical leads in SMM-based spintronic devices remains a ubiquitous challenge: interactions with metallic electrodes can drastically modify the SMM's properties by charge transfer or through changes in the molecular structure. Here, we probe electrical transport through individual Fe ₄ SMMs using a scanning tunnelling microscope at 0.5 K. Correlation of topographic and spectroscopic information permits identification of the spin excitation fingerprint of intact Fe ₄ molecules. Building from this, we find that the exchange coupling strength within the molecule's magnetic core is significantly enhanced. First-principles calculations support the conclusion that this is the result of confinement of the molecule in the two-contact junction formed by the microscope tip and the sample surface.

Abstract

The incorporation of single-molecule magnets into spintronic devices is often hindered by electronic or structural modifications. Here, the authors demonstrate how confinement of Fe ₄ molecules in junctions between a Cu ₂N substrate and a scanning microscope tip enhances intra-molecular exchange interaction.