Permanent magnetism in phosphine- and chlorine-capped gold: from clusters to nanoparticles
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Magnetometry results have shown that gold NPs (∼2 nm in size) protected with phosphine and chlorine ligands exhibit permanent magnetism. When the NPs size decreases down to the subnanometric size range, e.g. undecagold atom clusters, the permanent magnetism disappears. The near edge structure of the X-ray absorption spectroscopy data points out that charge transfer between gold and the capping system occurs in both cases. These results strongly suggest that nearly metallic Au bonds are also required for the induction of a magnetic response. Electron paramagnetic resonance observations indicate that the contribution to magnetism from eventual iron impurities can be disregarded.
KeywordsGold clusters Gold nanoparticles EPR spectroscopy SQUID magnetometry Ferromagnetic behaviour
The authors would like to acknowledge the support of the European Synchrotron Radiation Facility and BM29 beamline staff. This research has been supported by the Spanish Ministry of Science ‘Ministerio de Ciencia e Innovación (MICINN)’ (Strategic Action NAN2004-09125-C07) and the Andalusian Government ‘Junta de Andalucía’ (Excellence Project P06-FQM-02254 and P09-FQM-4554, group TEP127). M.A. Muñoz-Márquez thanks the Spanish Research Council ‘Consejo Superior de Investigaciones Científicas (CSIC)’ I3P programme, E. Guerrero acknowledges the MICINN for financial support and R. Lucena thanks CSIC for a PhD grant.
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