RESEARCH ON OUR SITE
Changer la langue en Francais    SITE MAP | ACCESS | DIRECTORY | CONTACTS | PARTNERS | LINKS
  
 

Single Molecule Magnet, on the road to spintronic:

a major step forward achieved by DEIMOS scientists and their collaborators
SOLEIL Company Contents > All the news > News 2010 > Single Molecule Magnet, on the road to spintronic

DEIMOS scientists and associates from the IMPMC (Pierre et Marie Curie University), in collaboration with Roberta Sessoli research's group (Florence University), have succeeded in preparing oriented monolayer of single molecule magnet and, thanks to X-ray Magnetic Circular Dichroism measurements, have demonstrated that the magnetic properties and the quantum spin dynamics of these remarkable molecules were preserved.

Single Molecule Magnets (SMM) are organometallic compounds containing magnetic transition metal atoms organised by the organic ligands in a particular geometry that promotes large magnetic anisotropy (Figure 1). Thus the total magnetic moment of these molecules experiences a molecular anisotropy barrier which governs the relaxation and, at sufficiently low temperature (few degrees Kelvin and below), leads to magnetic remanence: hysteresis is observed upon cycling of the external magnetic field (figure 2).

Figure 1

Scheme of a SMM from the dodecamanganese family, ground spin state S=10
Scheme of a SMM from the dodecamanganese family (Mn12), ground spin state S=10

Scheme of a SMM from the iron-four family, ground spin state S=5
Scheme of a SMM from the iron-four family (Fe4), ground spin state S=5

Courbes d’aimantation obtenues par mesures micro-SQUID d’un monocristal d’une molécule-aimant de la famille des fer-quatre Figure 2: Magnetic hysteresis loops recorded by micro-SQUID on single crystal of a SMM from Fe4 family, [Fe4(OEt)3(L)(dpm)6; Cf. JACS 128, 4742-4755 (2006)], at constant field-sweep rate and different temperatures.
SMM may therefore be used for memory storage applications, but the more remarkable asset is the step like profile of the hysteresis curves due to quantum tunnelling of the spin reversal. This makes SMM very promising candidates for molecular spintronic, e.g. logical quantum gate applications, assuming they can be isolated.

Représentation d’une molécule de la famille des fer-quatre fonctionnalisée pour la préparation

Figure 3: Scheme of a SMM from Fe4 family functionalized for self assembled monolayer synthesis.

A significant step forward has been achieved recently by showing that magnetic bistability of a class of SMM, Fe4, can be preserved upon monolayer self assembly on Au (111) surface (figure 3). These results have been obtained thanks to X-ray Magnetic Circular Dichroism (XMCD) experiments performed at European synchrotrons radiations centers (SIM beamline at SLS and ID08 at ESRF [Cf. Mannini et al. Nature Materials 8, 194–197 (2009)].

In the present letter to NATURE, the authors exploit the hysteresis curves angular dependence obtained at very low temperatures (500mK) to characterize the orientation of Fe4 molecules inside the self assembled monolayer. By probing the magnetic quantum tunnelling using XMCD, they demonstrate that molecular ordering on surface leads to coupling of the crystalline anisotropy with the magnetic anisotropy. These outstanding results are bringing SMM even closer to molecular spintronic and potentially quantum computing [DOI 10.1038/nature09478, in NATURE November 18th, 2010].
 
 
Reference :

M. Mannini, F. Pineider, C. Danieli, F. Totti, L. Sorace, Ph. Sainctavit, M.-A. Arrio, E. Otero, L. Joly, J. Criginski Cezar, A. Cornia, and R. Sessoli.
Quantum tunnelling of the magnetization in a monolayer of oriented single-molecule magnets.
Letter to Nature, 2010, vol 468, p 417-421.

 
 Web site of 
DEIMOS beamline

 DEIMOS publications
Accueil