PolLux: A new facility for soft x-ray spectromicroscopy at the Swiss Light Source

Raabe, Jörg; Tzvetkov, George; Flechsig, U.; Böge, M.; Jaggi, A.; Sarafimov, B.; Vernooij, Martine G.C.; Huthwelker, Thomas; Ade, Harald; Kilcoyne, A. L. D.; Tyliszczak, Tolek; Fink, R.; Quitmann, C.

doi:10.1063/1.3021472

Cited by 237 publications

(205 citation statements)

References 48 publications

(41 reference statements)

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“…Imaging was performed in bright field mode. Microspectroscopy measurements were performed using the PolLux STXM microscope at the Swiss Light Source (SLS) (22). Typical STXM transmission images of atmospheric diesel or wood combustion particles recorded at 300 eV (after the C K-edge) are presented in Figure 1.…”

Section: Emission Samplesmentioning

confidence: 99%

On Source Identification and Alteration of Single Diesel and Wood Smoke Soot Particles in the Atmosphere; An X-Ray Microspectroscopy Study

Vernooij

Mohr

Tzvetkov

et al. 2009

Environ. Sci. Technol.

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Diesel and wood combustion are major sources of carbonaceous particles in the atmosphere. It is very hard to distinguish between the two sources by looking at soot particle morphology, but clear differences in the chemical structure of single particles are revealed by C(1s) NEXAFS (near edge X-ray absorption fine structure) microspectroscopy. Soot from diesel combustion has a dominant spectral signature at ∼285 eV from aromatic π-bonds, whereas soot from wood combustion has the strongest signature at ∼287 eV from phenolic carbon bonds. To investigate if it is possible to use these signatures for source apportionment purposes, we collected atmospheric samples with either diesel or wood combustion as a dominant particle source. No spectra obtained from the atmospheric particles completely matched the emission spectra. Especially particles from the wood dominated location underwent large modifications; the phenolic spectral signature at ∼287 eV is greatly suppressed and surpassed by the peak attributed to the aromatic carbon groups at ∼285 eV. Comparison with spectra from diesel soot samples experimentally aged with ozone show that very fast modification of the carbon structure of soot particles occurs as soon as they enter the atmosphere. Source attribution of single soot particles with microspectroscopy is thus hardly possible, but NEXAFS remains a powerful tool to study aging effects.

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Section: Emission Samplesmentioning

confidence: 99%

On Source Identification and Alteration of Single Diesel and Wood Smoke Soot Particles in the Atmosphere; An X-Ray Microspectroscopy Study

Vernooij

Mohr

Tzvetkov

et al. 2009

Environ. Sci. Technol.

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“…The most prominent concern the actual timescale and physical processes that govern the magnetization dynamics during and after current injection, the initial and intermediate magnetic configuration preceding switching, as well as the role played by the DL and FL components of the torque and the DMI. Here, we report the direct observation of the dynamics excited by SOTs during the switching process by performing current-pump and x-ray probe experiments in the time domain using a scanning transmission x-ray microscope (STXM) 40 . Our measurements reveal the evolution of the nanoscale magnetization from the initial domain nucleation stage to full or partial switching, depending on the duration and amplitude of the current pulses.…”

mentioning

confidence: 99%

Spatially and time-resolved magnetization dynamics driven by spin–orbit torques

et al. 2017

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Current-induced spin-orbit torques (SOTs) represent one of the most effective ways to manipulate the magnetization in spintronic devices. The orthogonal torquemagnetization geometry, the strong damping, and the large domain wall velocities inherent to materials with strong spin-orbit coupling make SOTs especially appealing for fast switching applications in nonvolatile memory and logic units. So far, however, the timescale and evolution of the magnetization during the switching process have remained undetected. Here, we report the direct observation of SOTdriven magnetization dynamics in Pt/Co/AlO x dots during current pulse injection.Time-resolved x-ray images with 25 nm spatial and 100 ps temporal resolution reveal that switching is achieved within the duration of a sub-ns current pulse by the fast nucleation of an inverted domain at the edge of the dot and propagation of a tilted domain wall across the dot. The nucleation point is deterministic and alternates between the four dot quadrants depending on the sign of the magnetization, current, and external field. Our measurements reveal how the magnetic symmetry is broken by the concerted action of both damping-like and field-like SOT and show that reproducible switching events can be obtained for over 10 12 reversal cycles. arXiv:1704.06402v1 [cond-mat.mtrl-sci] 21 Apr 2017Controlling the magnetic state of ultrathin heterostructures using electric currents is key to developing nonvolatile memory devices with minimal static and dynamic power consumption 1 . A promising approach for magnetic switching is based on injecting an in-plane current into a ferromagnet/heavy metal bilayer, where the spin-orbit torques (SOTs) 2,3 resulting from the spin Hall effect and interface charge-spin conversion 4-8 provide an efficient mechanism to reverse the magnetization 1,9,10,12-15 and manipulate domain walls (DWs) [16][17][18][19] .SOT switching schemes can be easily integrated into three-terminal magnetic tunnel junctions having either in-plane 10 or out-of-plane 20 magnetization. Although the threeterminal geometry is more demanding in terms of size, it offers desirable features compared to the two-terminal spin-transfer torque (STT) approach presently used in magnetic random access memories (MRAM) 21 . One such feature is the separation of the read and write current paths in the tunnel junction, which avoids electrical stress of the oxide barrier during writing and allows for independent optimization of the tunneling magnetoresistance during reading. The other crucial feature is the switching speed, which is expected to be extremely fast because the spin accumulation inducing the SOTs is orthogonal to the quiescent magnetization, leading to a negligible incubation delay. Such a delay is a major issue for STT devices, since thermal fluctuations result in a switching time distribution that is several ns wide 22,23 . Furthermore, the SOT-induced magnetization dynamics is governed by strong damping in the monodomain regime 24,25 and fast domain wall motion in the m...

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“…The STXM and NEXAFS analyses were performed at the PolLux beamline (Raabe et al, 2008) of the Swiss Light Source (SLS) located at the Paul Scherrer Institute. Photons in the range of 200-1200 eV are provided by this beamline with an energy resolution (E/ E) of about 3000.…”

Section: Stxm-nexafs Analysismentioning

confidence: 99%

Aging induced changes on NEXAFS fingerprints in individual combustion particles

et al. 2011

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Abstract. Soot particles can significantly influence the Earth's climate by absorbing and scattering solar radiation as well as by acting as cloud condensation nuclei. However, despite their environmental (as well as economic and political) importance, the way these properties are affected by atmospheric processing of the combustion exhaust gases is still a subject of discussion. In this work, individual soot particles emitted from two different vehicles, a EURO 2 transporter, a EURO 3 passenger car, and a wood stove were investigated on a single-particle basis. The emitted exhaust, including the particulate and the gas phase, was processed in a smog chamber with artificial solar radiation. Single particle specimens of both unprocessed and aged soot were characterized using near edge X-ray absorption fine structure spectroscopy (NEXAFS) and scanning electron microscopy. Comparison of NEXAFS spectra from the unprocessed particles and those resulting from exhaust photooxidation in the chamber revealed changes in the carbon functional group content. For the wood stove emissions, these changes were minor, related to the relatively mild oxidation conditions. For the EURO 2 transporter emissions, the most apparent change was that of carboxylic carbon from oxidized organic compounds condensing on the primary soot particles. For the EURO 3 car emissions oxidation of primary soot particles upon photochemical aging has likely contributed as well. Overall, Correspondence to: M. Ammann (markus.ammann@psi.ch) the changes in the NEXAFS fingerprints were in qualitative agreement with data from an aerosol mass spectrometer. Furthermore, by taking full advantage of our in situ microreactor concept, we show that the soot particles from all three combustion sources changed their ability to take up water under humid conditions upon photochemical aging of the exhaust. Due to the selectivity and sensitivity of the NEXAFS technique for the water mass, also small amounts of water taken up into the internal voids of agglomerated particles could be detected. Because such small amounts of water uptake do not lead to measurable changes in particle diameter, it may remain beyond the limits of volume growth measurements, especially for larger agglomerated particles.

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PolLux: A new facility for soft x-ray spectromicroscopy at the Swiss Light Source

Cited by 237 publications

References 48 publications

On Source Identification and Alteration of Single Diesel and Wood Smoke Soot Particles in the Atmosphere; An X-Ray Microspectroscopy Study

On Source Identification and Alteration of Single Diesel and Wood Smoke Soot Particles in the Atmosphere; An X-Ray Microspectroscopy Study

Spatially and time-resolved magnetization dynamics driven by spin–orbit torques

Aging induced changes on NEXAFS fingerprints in individual combustion particles

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