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Title: Magnetic Ordering in Gold Nanoclusters

Abstract

Here, several research groups have observed magnetism in monolayer-protected gold-cluster samples, but the results were often contradictory and thus a clear understanding of this phenomenon is still missing. We used Au 25(SCH 2CH 2Ph) 18 0, which is a paramagnetic cluster that can be prepared with atomic precision and whose structure is known precisely. Previous magnetometry studies only detected paramagnetism. We used samples representing a range of crystallographic orders and studied their magnetic behaviors by electron paramagnetic resonance (EPR). As a film, Au 25(SCH 2CH 2Ph) 18 0 displays paramagnetic behavior but, at low temperature, ferromagnetic interactions are detectable. One or few single crystals undergo physical reorientation with the applied field and display ferromagnetism, as detected through hysteresis experiments. A large collection of microcrystals is magnetic even at room temperature and shows distinct paramagnetic, superparamagnetic, and ferromagnetic behaviors. Simulation of the EPR spectra shows that both spin-orbit coupling and crystal distortion are important to determine the observed magnetic behaviors. DFT calculations carried out on single cluster and periodic models predict values of spin6orbit coupling and crystal6splitting effects in agreement with the EPR derived quantities. Magnetism in gold nanoclusters is thus demonstrated to be the outcome of a very delicate balancemore » of factors. To obtain reproducible results, the samples must be (i) controlled for composition and thus be monodispersed with atomic precision, (ii) of known charge state, and (iii) well defined also in terms of crystallinity and experimental conditions. This study highlights the efficacy of EPR spectroscopy to provide a molecular understanding of these phenomena« less

Authors:
 [1];  [1];  [1];  [1];  [1]; ORCiD logo [2];  [2]; ORCiD logo [3];  [3]; ORCiD logo [4]
  1. Univ. of Padova, Padova (Italy)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. CNR-ICCOM & IPCF, Pisa (Italy)
  4. Univ. of Padova, Padova (Italy); Univ. of Connecticut, Storrs, CT (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1363986
Report Number(s):
PNNL-SA-125554
Journal ID: ISSN 2470-1343; 49645; KP1704020
Grant/Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Omega
Additional Journal Information:
Journal Volume: 2; Journal Issue: 6; Journal ID: ISSN 2470-1343
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Environmental Molecular Sciences Laboratory; Crystal structure; Magnetic properties; Mechanical properties; Nanoclusters; Physical and chemical processes

Citation Formats

Agrachev, Mikhail, Antonello, Sabrina, Dainese, Tiziano, Ruzzi, Marco, Zoleo, Alfonso, Apra, Edoardo, Govind, Niranjan, Fortunelli, Alessandro, Sementa, Luca, and Maran, Flavio. Magnetic Ordering in Gold Nanoclusters. United States: N. p., 2017. Web. doi:10.1021/acsomega.7b00472.
Agrachev, Mikhail, Antonello, Sabrina, Dainese, Tiziano, Ruzzi, Marco, Zoleo, Alfonso, Apra, Edoardo, Govind, Niranjan, Fortunelli, Alessandro, Sementa, Luca, & Maran, Flavio. Magnetic Ordering in Gold Nanoclusters. United States. doi:10.1021/acsomega.7b00472.
Agrachev, Mikhail, Antonello, Sabrina, Dainese, Tiziano, Ruzzi, Marco, Zoleo, Alfonso, Apra, Edoardo, Govind, Niranjan, Fortunelli, Alessandro, Sementa, Luca, and Maran, Flavio. Mon . "Magnetic Ordering in Gold Nanoclusters". United States. doi:10.1021/acsomega.7b00472. https://www.osti.gov/servlets/purl/1363986.
@article{osti_1363986,
title = {Magnetic Ordering in Gold Nanoclusters},
author = {Agrachev, Mikhail and Antonello, Sabrina and Dainese, Tiziano and Ruzzi, Marco and Zoleo, Alfonso and Apra, Edoardo and Govind, Niranjan and Fortunelli, Alessandro and Sementa, Luca and Maran, Flavio},
abstractNote = {Here, several research groups have observed magnetism in monolayer-protected gold-cluster samples, but the results were often contradictory and thus a clear understanding of this phenomenon is still missing. We used Au25(SCH2CH2Ph)180, which is a paramagnetic cluster that can be prepared with atomic precision and whose structure is known precisely. Previous magnetometry studies only detected paramagnetism. We used samples representing a range of crystallographic orders and studied their magnetic behaviors by electron paramagnetic resonance (EPR). As a film, Au25(SCH2CH2Ph)180 displays paramagnetic behavior but, at low temperature, ferromagnetic interactions are detectable. One or few single crystals undergo physical reorientation with the applied field and display ferromagnetism, as detected through hysteresis experiments. A large collection of microcrystals is magnetic even at room temperature and shows distinct paramagnetic, superparamagnetic, and ferromagnetic behaviors. Simulation of the EPR spectra shows that both spin-orbit coupling and crystal distortion are important to determine the observed magnetic behaviors. DFT calculations carried out on single cluster and periodic models predict values of spin6orbit coupling and crystal6splitting effects in agreement with the EPR derived quantities. Magnetism in gold nanoclusters is thus demonstrated to be the outcome of a very delicate balance of factors. To obtain reproducible results, the samples must be (i) controlled for composition and thus be monodispersed with atomic precision, (ii) of known charge state, and (iii) well defined also in terms of crystallinity and experimental conditions. This study highlights the efficacy of EPR spectroscopy to provide a molecular understanding of these phenomena},
doi = {10.1021/acsomega.7b00472},
journal = {ACS Omega},
number = 6,
volume = 2,
place = {United States},
year = {Mon Jun 12 00:00:00 EDT 2017},
month = {Mon Jun 12 00:00:00 EDT 2017}
}

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