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Int. J. Mol. Sci. 2013, 14(9), 17618-17642; doi:10.3390/ijms140917618
Article

Spin Polarization and Quantum Spins in Au Nanoparticles

,
,
 and *
Department of Physics and Center for Neutron Beam Applications, National Central University, Jhongli 32001, Taiwan
* Author to whom correspondence should be addressed.
Received: 4 July 2013 / Revised: 1 August 2013 / Accepted: 5 August 2013 / Published: 28 August 2013
(This article belongs to the Special Issue Magnetic Nanoparticles 2013)
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Abstract

The present study focuses on investigating the magnetic properties and the critical particle size for developing sizable spontaneous magnetic moment of bare Au nanoparticles. Seven sets of bare Au nanoparticle assemblies, with diameters from 3.5 to 17.5 nm, were fabricated with the gas condensation method. Line profiles of the X-ray diffraction peaks were used to determine the mean particle diameters and size distributions of the nanoparticle assemblies. The magnetization curves M(Ha) reveal Langevin field profiles. Magnetic hysteresis was clearly revealed in the low field regime even at 300 K. Contributions to the magnetization from different size particles in the nanoparticle assemblies were considered when analyzing the M(Ha) curves. The results show that the maximum particle moment will appear in 2.4 nm Au particles. A similar result of the maximum saturation magnetization appearing in 2.3 nm Au particles is also concluded through analysis of the dependency of the saturation magnetization MP on particle size. The MP(d) curve departs significantly from the 1/d dependence, but can be described by a log-normal function. Magnetization can be barely detected for Au particles larger than 27 nm. Magnetic field induced Zeeman magnetization from the quantum confined Kubo gap opening appears in Au nanoparticles smaller than 9.5 nm in diameter.
Keywords: Au nanoparticle; spontaneous particle moment; field induced Zeeman magnetization Au nanoparticle; spontaneous particle moment; field induced Zeeman magnetization
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Li, C.-Y.; Karna, S.K.; Wang, C.-W.; Li, W.-H. Spin Polarization and Quantum Spins in Au Nanoparticles. Int. J. Mol. Sci. 2013, 14, 17618-17642.

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