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00925njm 22002777a 4500 dc Crespo del Arco, Patricia author Litran, R. author Rojas, T. C. author Multigner, M. author De la Fuente, J. M. author Sánchez López, J. C. author Garcia, M. A. author Hernando Grande, Antonio author Penadés, S. author Fernández, A. author 2004-08-20 We report on the experimental observation of magnetic hysteresis up to room temperature in thiol-capped Au nanoparticles with 1.4 nm size. The coercive field ranges from 860 Oe at 5 K to 250 Oe at 300 K. It is estimated that the Au atoms exhibit a magnetic moment of mu=0.036mu(B). However, Au nanoparticles with similar size but stabilized by means of a surfactant, i.e., weak interaction between protective molecules and Au surface atoms, are diamagnetic, as bulk Au samples are. The apparent ferromagnetism is consequently associated with 5d localized holes generated through Au-S bonds. These holes give rise to localized magnetic moments that are frozen in due to the combination of the high spin-orbit coupling (1.5 eV) of gold and the symmetry reduction associated with two types of bonding: Au-Au and Au-S. 0031-9007 10.1103/PhysRevLett.93.087204 https://hdl.handle.net/20.500.14352/52018 http://dx.doi.org/10.1103/PhysRevLett.93.087204 http://journals.aps.org Permanent magnetism, magnetic anisotropy, and hysteresis of thiol-capped gold nanoparticles