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Wednesday, 19 October 2011

Single molecule magnets couple up. PHYS. REV. LETT. 107 (2011)

According to ICN group leader and ICREA Prof. Pietro Gambardella, single molecule magnets behaving as coupled but separate magnetic units from a ferromagnetic substrate raise the possibility of incorporating them into hybrid molecule/metal devices where each molecule stores a single bit of information.

As published in the 2011 October volume of Physical Review Letters, researchers of the ICN Atomic Manipulation and Spectroscopy Group led by Prof. Pietro Gambardella have shown that single molecule magnets in contact with a ferromagnetic electrode behave as coupled but separate magnetic units from the substrate. The strength of the molecule-substrate coupling can be tuned by electron or hole doping of the interface, adding chemical functionality to such systems. These observations have raised hopes to incorporate tiny single molecule magnetic elements into hybrid molecular –metal circuits.

With dimensions close to 1 nanometer, molecules that possess bi-stable magnetic states represent the ultimate in digital storage media. Their usefulness to fabricate molecular memories, however, is limited by the instability of their magnetic moment in response to thermal fluctuations.

The study carried out by the ICN Atomic Manipulation and Spectroscopy Group shows that single molecule magnets can be made more stable by grafting them to ferromagnetic metal films, which induces antiparallel coupling of the molecule magnetisation to that of the underlying substrate. The Group used the absorption of circularly polarized x-rays at the European Synchrotron Radiation facility in Grenoble to probe the molecule/metal layers in an element specific way. It was shown that, depending on the strength and direction of an applied magnetic field, both antiparallel and parallel magnetic configurations can be reached, which is a prerequisite to construct the molecular analogue of a spin valve device. Further, the strength of the molecule-substrate coupling can be tuned by electron or hole doping of the interface, which adds chemical functionality to such systems. These observations raise hopes to incorporate tiny single molecule magnetic elements into hybrid molecular-metal circuits.

This experiment shows that single molecule magnets in contact with a ferromagnetic electrode behave as coupled but separate magnetic units from the substrate, which raises hopes to incorporate them into hybrid molecule/metal devices.

Atomic Manipulation and Spectroscopy Group

Physical Review Letters