Exploring nanoscale magnetism in advanced materials with polarized X-rays

Fischer, Peter

doi:10.1016/j.mser.2011.03.002

Cited by 18 publications

(8 citation statements)

References 215 publications

(117 reference statements)

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“…However, an out-of-equilibrium core generates sufficient magnetostatic energy to dynamically couple neighbor vortices, as demonstrated in some very recent studies. [8][9][10][11][12][13][14][15][16] Particularly interesting is the fact that it is possible to transfer energy, with negligible loss, between two neighbor vortices by stimulated gyrotropic motion. 9 This dynamic coupling is strongly dependent on the distance d between the centers of the vortices.…”

Section: Introductionmentioning

confidence: 99%

Magnetic vortex echoes

García

Sinnecker

Novais

et al. 2012

Journal of Applied Physics

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The dynamic properties of magnetic vortices have many potential applications in fast magnetic devices. Here we present a micromagnetic study of the motion of magnetic vortices in arrays of 100 nanodisks that have a normal distribution of diameters, as expected in real array systems, e.g., produced by nanolithography. The micromagnetic simulated experiments follow a protocol with an initial preparation and magnetic pulses that enable the control of the magnetic vortices initial positions and circular motion direction. The results show a new effect-the magnetic vortex echo (MVE) that arises from the refocusing of the overall array magnetization. We show, by using arrays with different interdisk separations, that MVE affords a means of characterizing them as regards the homogeneity and intensity of the interaction between its elements, properties that are relevant for device applications. We also show that a simple analytical model, analogous to the one that describes the spin echo in magnetic resonance, can be used to explain most features of the simulated magnetic vortex echo. V

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Section: Introductionmentioning

confidence: 99%

Magnetic vortex echoes

García

Sinnecker

Novais

et al. 2012

Journal of Applied Physics

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“…Structural characterization of as-prepared core-shell nanoparticles In order to determine how the elements forming the core and shell are spatially distributed within the ligand-capped nanoparticles, the powdered samples were analyzed using transmission soft X-ray microscopy (TXM) at the Advanced Light Source (ALS) in Berkeley, CA. 43,44 In TXM, the spatial resolution is obtained through Fresnel zone plate optical elements, and recently a 15 nm spatial resolution has been reported. 45 The standard resolution, which was also achieved in this experiment, is currently B25 nm.…”

Section: Resultsmentioning

confidence: 99%

“…High spatial resolution imaging down to 25 nm with soft X-rays providing element specific information was performed at the full-field soft X-ray microscope XM-1 which is located at beamline 6.1.2 at the Advanced Light Source (ALS) in Berkeley, CA. 43 UV-Visible spectroscopy measurements were performed using a Varian Cary 5000 spectrophotometer. A halogen incandescent lamp was used to study the optical properties in the wavelength range of 400-1000 nm using a 1 cm path length quartz cuvette at room temperature.…”

Section: Characterizationmentioning

confidence: 99%

A DRIFTS study of CO adsorption and hydrogenation on Cu-based core–shell nanoparticles

Subramanian

Kumar

Watanabe

et al. 2012

Catal. Sci. Technol.

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Core-shell nanoparticles are being considered for various applications due to their controllable atomic structure and improved properties compared to their bulk counterparts. In the present work, we have synthesized Cu@Mn 3 O 4 and Cu@Co 3 O 4 (core@shell) nanocatalysts using wet-chemical synthesis methods involving organic surfactants, and probed their surfaces using CO and H 2 under reaction conditions using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The surfactant ligands used in the synthesis of the nanoparticles must be removed to allow access to the active catalyst sites. These ligands can be removed by oxidation, allowing adsorption of CO and H 2 . This work reports the DRIFTS results of CO adsorption and hydrogenation on Cu@Mn 3 O 4 and Cu@Co 3 O 4 nanoparticles after removing the ligands. The CO hydrogenation results were in agreement with the DRIFTS results, which suggested that the Cu@Co 3 O 4 nanoparticles adsorb CO both dissociatively and associatively, creating a balance between molecular CO required for CO insertion and dissociated surface carbon species required for chain growth. This resulted in higher selectivities towards C 2+ alcohols on this catalyst. On the other hand, the Cu@Mn 3 O 4 nanoparticles showed a higher CO uptake and a lower CO dissociation activity, which resulted in a lower CH x concentration on the surface, thus limiting the rate of the CO insertion step required to form higher alcohols.

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“…In the soft-X-ray region, magnetic microscopy has been performed with full-field 176,177) and scanning X-ray imaging. 178) Both types of microscopes use FZPs to achieve a spatial resolution better than 20 nm.…”

Section: Micro Xmcd Magnetometry In Bit-patterned Mediamentioning

confidence: 99%

Recent Progress of the X-ray Magnetic Circular Dichroism Technique for Element-Specific Magnetic Analysis

Nakamura

Suzuki

2013

J. Phys. Soc. Jpn.

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Recent trend of the X-ray magnetic circular dichroism (XMCD) spectroscopy-based technique and the related scientific topics at SPring-8 are reviewed. At the third-generation synchrotron radiation facility, the key developments in the XMCD technique include i) significant improvements in the accuracy and sensitivity of XMCD measurements with a quick helicity switching of circularly polarized X-rays, ii) introduction of extreme conditions (strong pulsed magnetic field and high pressures), and iii) new experimental setup using the high-brilliance X-ray source (microfocusing, reflection geometry, and high-pressure cells). These achievements have effectively extended the capability of the XMCD technique, a unique magnetic probe with an element-specificity, providing fundamental scientific insights in spintronics and magnetic recording devices, magnetic nanoparticles, and magnetism under high-magnetic field and high pressures.KEYWORDS: X-ray magnetic circular dichroism, element specific magnetic hysteresis, synchrotron radiation X-rays Historical ReviewElement-specific magnetic measurements are widely recognized as a powerful experimental technique for the study of magnetic materials and have previously been exploited mainly by Mössbauer spectroscopy. For the last 30 years, an energy-tunable and polarized X-ray source at synchrotron radiation facilities has given rather expansive possibilities of element-specific magnetic measurements using X-ray spectroscopy. Indeed, X-ray magnetic circular dichroism (XMCD) spectroscopy 1,2) has become one of the leading techniques for element-specific magnetic measurement using a resonant effect in the core-shell absorption with circularly polarized X-ray photons.The XMCD effect was first observed at the Fe K edge in the hard-X-ray region in 1987 by Schütz et al.3) In their experiment, an XMCD spectrum of pure iron was obtained by reversing the direction of magnetic fields applied to a sample, and the circularly polarized X-rays were provided by the off-orbital radiation from a bending magnet (off-plane method).3) The recorded XMCD signal was quite small, of the order of ÁI=I $ 5 Â 10 À3 . Subsequently, XMCD spectra at the L 2;3 edges of rare-earth elements [4][5][6] and at the L 2;3 edges of 5d metals in some alloys with 3d transition metals were also reported. 7) XMCD measurements over a wide energy range that is similar to the extended X-ray absorption fine structure (EXAFS), called magnetic EXAFS, in Fe and Gd 3 Fe 5 O 12 showed a capability of analyses of local magnetic structures using dichroic effects. 8,9) In the soft-X-ray region, the first XMCD spectrum at the Ni L 2;3 edges in a Ni single crystal was reported by Chen et al. in 1990. 10) The circularly polarized soft X-rays were obtained by the off-plain method, similar to the previous XMCD measurement at the Fe K edge.3) The intensity of the observed XMCD signal was about 8% with respect to the resonant absorption, the so called white line, and was much larger than that recorded at the K edge. The strong XMCD value at the...

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Exploring nanoscale magnetism in advanced materials with polarized X-rays

Cited by 18 publications

References 215 publications

Magnetic vortex echoes

Magnetic vortex echoes

A DRIFTS study of CO adsorption and hydrogenation on Cu-based core–shell nanoparticles

Recent Progress of the X-ray Magnetic Circular Dichroism Technique for Element-Specific Magnetic Analysis

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