%0 Journal Article
%A Crespo del Arco, Patricia
%A Litran, R.
%A Rojas, T. C.
%A Multigner, M.
%A De la Fuente, J. M.
%A Sánchez López, J. C.
%A Garcia, M. A.
%A Hernando Grande, Antonio
%A Penadés, S.
%A Fernández, A.
%T Permanent magnetism, magnetic anisotropy, and hysteresis of thiol-capped gold nanoparticles
%D 2004
%@ 0031-9007
%U https://hdl.handle.net/20.500.14352/52018
%X 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.
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