Magnetic memory of a single-molecule quantum magnet wired to a gold surface

Abstract

In the field of molecular spintronics1, the use of magnetic molecules for information technology is a main target and the observation of magnetic hysteresis on individual molecules organized on surfaces is a necessary step to develop molecular memory arrays. Although simple paramagnetic molecules can show surface-induced magnetic ordering and hysteresis when deposited on ferromagnetic surfaces2, information storage at the molecular level requires molecules exhibiting an intrinsic remnant magnetization, like the so-called single-molecule magnets3 (SMMs). These have been intensively investigated for their rich quantum behaviour4 but no magnetic hysteresis has been so far reported for monolayers of SMMs on various non-magnetic substrates, most probably owing to the chemical instability of clusters on surfaces5. Using X-ray absorption spectroscopy and X-ray magnetic circular dichroism synchrotron-based techniques, pushed to the limits in sensitivity and operated at sub-kelvin temperatures, we have now found that robust, tailor-made Fe4 complexes retain magnetic hysteresis at gold surfaces. Our results demonstrate that isolated SMMs can be used for storing information. The road is now open to address individual molecules wired to a conducting surface6,7 in their blocked magnetization state, thereby enabling investigation of the elementary interactions between electron transport and magnetism degrees of freedom at the molecular scale8,9.

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Figure 1: Monolayer of Fe4 on gold.
Figure 2: XAS/XMCD of Fe4 monolayer.
Figure 3: Hysteresis and magnetization dynamics of Fe4 monolayer.

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Acknowledgements

We acknowledge F. Scheurer, J. P. Kappler and B. Muller for their help in the installation of the endstation, and the staff of the X11MA-SIM (Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland) and UE46-PGM (BESSY synchrotron, Berlin, Germany) beamlines for their support. In particular, we thank A. Fraile-Rodriguez, L. Joly and F. Nolting for their excellent technical support at the X11MA-SIM beamline. We thank L. Gorini for his contribution to the development of the ligand synthesis and M. Etienne for his help in artwork preparation. This research project has been supported by the EU, within the EU FP6, through the Key Action: Strengthening the European Research Area, Research Infrastructures, through NoE MAGMANet, through the Integrated Infrastructure Initiative ‘Integrating Activity on Synchrotron and Free Electron Laser Science’ and through the ERANET project ‘NanoSci-ERA: NanoScience in the European Research Area’. It has been partially financially supported by the Italian CNR and MIUR and by the German DFG.

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Correspondence to Roberta Sessoli.

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Mannini, M., Pineider, F., Sainctavit, P. et al. Magnetic memory of a single-molecule quantum magnet wired to a gold surface. Nature Mater 8, 194–197 (2009) doi:10.1038/nmat2374

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