Open AccessPermanent Magnetism, Magnetic Anisotropy, and Hysteresis of Thiol-Capped Gold Nanoparticles
Author(s) -
P. Crespo,
R. Litrán,
T.C. Rojas,
M. Multigner,
Jesús M. de la Fuente,
J.C. Sánchez-López,
M. A. Garcı̀a,
A. Hernando,
S. PENADES,
A. Fernández
Publication year - 2004
Publication title -
physical review letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.688
H-Index - 673
eISSN - 1079-7114
pISSN - 0031-9007
DOI - 10.1103/physrevlett.93.087204
Subject(s) - diamagnetism , materials science , magnetic moment , magnetism , condensed matter physics , magnetic anisotropy , ferromagnetism , coercivity , hysteresis , nanoparticle , magnetic hysteresis , magnetization , nanotechnology , magnetic field , physics , quantum mechanics
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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