Magnetic Bistability of Individual Single-Molecule Magnets Grafted on Single-Wall Carbon Nanotubes

摘要

Magnetic bistability has already been observed and widely investigated for magnetic complexes called single-molecule magnets (SMMs). This behavior, observed at the level of a crystal, is due to specific molecular properties, that is, the presence of a high-spin ground state and an easy axis of magnetization for the individual molecules assembled within the crystal. For the design of information storage devices based on single magnetic molecules (albeit at very low temperatures), one major challenge is to confirm the presence of magnetic bistability at the level of individual molecules. The first studies focused on archetypal Mn_(12) SMMs. Unfortunately, because of the relatively weak stability of this family of compounds and the very high sensitivity of the orientation of the easy axis of magnetization towards the environment, no magnetic hysteresis was observed when the molecules were anchored on surfaces. Chemical stability and particularly robustness against deformation are necessary to maintain the magnetic bistability in isolated SMMs, especially when the molecules are electronically coupled to a surface. Very recently, using X-ray magnetic circular dichroism and focusing on a tetranuclear Fe~(III) complex (Fe_4) grafted on gold, Sessoli and co-workers gave the first evidence of the presence of a magnetic hysteresis loop associated with isolated molecules. Another important issue is the investigation of the synergy between electron transport and the magnetic properties of the SMMs, which may eventually be exploited for addressing individual molecules. Assembling SMMs on carbon nanotubes (GNTs) is one of the most promising strategies to realize such synergy. One of us and his group studied the grafting of a compound of the Fe_4 family on CNTs, but no magnetic characterization of these devices has been reported.