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Vijayakumar, J.; Savchenko, T.M.; Bracher, D.M.; Lumbeeck, G.; Béché, A.; Verbeeck, J.; Vajda, Š.; Nolting, F.; Vaz, Ca.f.; Kleibert, A. |
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Title |
Absence of a pressure gap and atomistic mechanism of the oxidation of pure Co nanoparticles |
Type |
A1 Journal Article |
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Year  |
2023 |
Publication |
Nature communications |
Abbreviated Journal |
Nat Commun |
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Volume |
14 |
Issue |
1 |
Pages |
174 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT) |
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Abstract |
Understanding chemical reactivity and magnetism of 3<italic>d</italic>transition metal nanoparticles is of fundamental interest for applications in fields ranging from spintronics to catalysis. Here, we present an atomistic picture of the early stage of the oxidation mechanism and its impact on the magnetism of Co nanoparticles. Our experiments reveal a two-step process characterized by (i) the initial formation of small CoO crystallites across the nanoparticle surface, until their coalescence leads to structural completion of the oxide shell passivating the metallic core; (ii) progressive conversion of the CoO shell to Co<sub>3</sub>O<sub>4</sub>and void formation due to the nanoscale Kirkendall effect. The Co nanoparticles remain highly reactive toward oxygen during phase (i), demonstrating the absence of a pressure gap whereby a low reactivity at low pressures is postulated. Our results provide an important benchmark for the development of theoretical models for the chemical reactivity in catalysis and magnetism during metal oxidation at the nanoscale. |
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Wos |
000955726400021 |
Publication Date |
2023-01-12 |
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ISSN |
2041-1723 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
16.6 |
Times cited |
1 |
Open Access |
OpenAccess |
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Notes |
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, 200021160186 2002153540 ; EC | Horizon 2020 Framework Programme, 810310 823717 ; University of Basel | Swiss Nanoscience Institute, P1502 ; This work is funded by Swiss National Foundation (SNF) (Grants. No 200021160186 and 2002153540) and the Swiss Nanoscience Institut (SNI) (Grant No. SNI P1502). S.V. acknowledges support from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 810310, which corresponds to the J. Heyrovsky Chair project (“ERA Chair at J. Heyrovský Institute of Physical Chemistry AS CR – The institutional approach towards ERA”). The funders had no role in the preparation of the article. Part of this work was performed at the Surface/Interface: Microscopy (SIM) beamline of the Swiss Light Source (SLS), Paul Scherrer Institut, Villigen, Switzerland. We kindly acknowledge Anja Weber and Elisabeth Müller from PSI for their help in fabricating the sample markers. A.B. and J. Verbeeck received funding from the European Union’s Horizon 2020 Research Infrastructure – Integrating Activities for Advanced Communities under grant agreement No. 823717 – ESTEEM3 reported |
Approved |
Most recent IF: 16.6; 2023 IF: 12.124 |
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Call Number |
EMAT @ emat @c:irua:196738 |
Serial |
8804 |
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Author |
Savchenko, T.M.; Buzzi, M.; Howald, L.; Ruta, S.; Vijayakumar, J.; Timm, M.; Bracher, D.; Saha, S.; Derlet, P.M.; Béché, A.; Verbeeck, J.; Chantrell, R.W.; Vaz, C.A.F.; Nolting, F.; Kleibert, A. |
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Title |
Single femtosecond laser pulse excitation of individual cobalt nanoparticles |
Type |
A1 Journal article |
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Year |
2020 |
Publication |
Physical Review B |
Abbreviated Journal |
Phys Rev B |
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Volume |
102 |
Issue |
20 |
Pages |
205418 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
Laser-induced manipulation of magnetism at the nanoscale is a rapidly growing research topic with potential for applications in spintronics. In this work, we address the role of the scattering cross section, thermal effects, and laser fluence on the magnetic, structural, and chemical stability of individual magnetic nanoparticles excited by single femtosecond laser pulses. We find that the energy transfer from the fs laser pulse to the nanoparticles is limited by the Rayleigh scattering cross section, which in combination with the light absorption of the supporting substrate and protective layers determines the increase in the nanoparticle temperature. We investigate individual Co nanoparticles (8 to 20 nm in size) as a prototypical model system, using x-ray photoemission electron microscopy and scanning electron microscopy upon excitation with single femtosecond laser pulses of varying intensity and polarization. In agreement with calculations, we find no deterministic or stochastic reversal of the magnetization in the nanoparticles up to intensities where ultrafast demagnetization or all-optical switching is typically reported in thin films. Instead, at higher fluences, the laser pulse excitation leads to photo-chemical reactions of the nanoparticles with the protective layer, which results in an irreversible change in the magnetic properties. Based on our findings, we discuss the conditions required for achieving laser-induced switching in isolated nanomagnets. |
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000589602000005 |
Publication Date |
2020-11-16 |
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ISSN |
2469-9950 |
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Additional Links |
UA library record; WoS full record |
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Impact Factor |
3.7 |
Times cited |
1 |
Open Access |
OpenAccess |
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Notes |
This work received funding by the Swiss National Foundation (SNF) (Grants No. 200021160186 and No. 2002153540), the Swiss Nanoscience Institute (SNI) (Grant No. SNI P1502), the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 737093 (FEMTOTERABYTE), and the COST Action CA17123 (MAGNETOFON). Part of this work was performed at the SIM beamline of the Swiss Light Source (SLS), Paul Scherrer Institut, Villigen, Switzerland. Part of the simulations were undertaken on the VIKING cluster, which is a high-performance compute facility provided by the University of York. We kindly acknowledge Anja Weber from PSI for preparation of substrates with marker structures. A.B. and Jo Verbeeck acknowledge funding through FWO Project No. G093417N (“Compressed sensing enabling low dose imaging in transmission electron microscopy”) from the Flanders Research Fund. Jo Verbeeck acknowledges funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 823717 – ESTEEM3. S.S. acknowledges ETH Zurich Post-Doctoral fellowship and Marie Curie actions for people COFUND program.; esteem3JRA; esteem3reported |
Approved |
Most recent IF: 3.7; 2020 IF: 3.836 |
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Call Number |
EMAT @ emat @c:irua:174273 |
Serial |
6669 |
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