The multipurpose time-of-flight neutron reflectometer “Platypus” at Australia's OPAL reactor

James, M. R.; Nelson, Andrew; Holt, Stephen A.; Saerbeck, Thomas; Hamilton, W. A.; Klose, F.

doi:10.1016/j.nima.2010.12.075

Cited by 155 publications

(119 citation statements)

References 60 publications

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“…The surface morphology of the α-Fe 2 O 3 layer was studied ex situ using a NT-MDT Solver Pro-M atomic force microscope (AFM). Magnetic measurements were performed with a Quantum Design PPMS magnetometer using the vibrating sample magnetometer option where the thin film was in-plane field cooled (FC) in 20 kOe from 300 to 5 K. The neutron reflectometry experiments were performed on the D3 reflectometer located at the NRU reactor in Chalk River (Canada), and using the Platypus reflectometer 28 at the OPAL reactor in Sydney (Australia). D3 operates at a wavelength of 0.237 nm using a PG monochromator along with a PG filter to reduce the higher-order contributions of the monochromator, whereas Platypus is a time-of-flight reflectometer maintaining a polarized neutron beam in a 0.25-to 1.3-nm wavelength spectrum.…”

Section: Methodsmentioning

confidence: 99%

Exchange bias in a nanocrystalline hematite/permalloy thin film investigated with polarized neutron reflectometry

et al. 2012

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We investigated a hematite α-Fe2O3/permalloy Ni80Fe20 bilayer film where the antiferromagnetic layer consisted of small hematite grains in the 2 to 16 nm range. A pronounced exchange bias effect occurred below the blocking temperature of 40 K. The magnitude of exchange bias was enhanced relative to reports for identical compounds in large grain, epitaxial films. However, the blocking temperature was dramatically reduced. As the Néel temperature of bulk α-Fe2O3 is known to be very high (860 K), we attribute the lowtemperature onset of exchange bias to the well-known finite-size effect which suppresses the Morin transition for nanostructured hematite. Polarized neutron reflectometry was used to place an upper limit on the concentration and length scale of a layer of uncompensated moments at the antiferromagnetic interface. The data were found to be consistent with an induced magnetic region at the antiferromagnetic interface of 0.5-1.0 μB per Fe atom within a depth of 1-2 nm. The field dependence of the neutron spin-flip signal and spin asymmetry was analyzed in the biased state, and the first and second magnetic reversal were found to occur by asymmetric mechanisms. For the fully trained permalloy loop, reversal occurred symmetrically at both coercive fields by an in-plane spin rotation of ferromagnetic domains. We investigated a hematite α-Fe 2 O 3 /permalloy Ni 80 Fe 20 bilayer film where the antiferromagnetic layer consisted of small hematite grains in the 2 to 16 nm range. A pronounced exchange bias effect occurred below the blocking temperature of 40 K. The magnitude of exchange bias was enhanced relative to reports for identical compounds in large grain, epitaxial films. However, the blocking temperature was dramatically reduced. As the Néel temperature of bulk α-Fe 2 O 3 is known to be very high (860 K), we attribute the low-temperature onset of exchange bias to the well-known finite-size effect which suppresses the Morin transition for nanostructured hematite. Polarized neutron reflectometry was used to place an upper limit on the concentration and length scale of a layer of uncompensated moments at the antiferromagnetic interface. The data were found to be consistent with an induced magnetic region at the antiferromagnetic interface of 0.5-1.0 μ B per Fe atom within a depth of 1-2 nm. The field dependence of the neutron spin-flip signal and spin asymmetry was analyzed in the biased state, and the first and second magnetic reversal were found to occur by asymmetric mechanisms. For the fully trained permalloy loop, reversal occurred symmetrically at both coercive fields by an in-plane spin rotation of ferromagnetic domains.

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Section: Methodsmentioning

confidence: 99%

Exchange bias in a nanocrystalline hematite/permalloy thin film investigated with polarized neutron reflectometry

et al. 2012

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“…In situ FMR and PNR measurements were carried out as a function of external hydrogen gas pressure at the PLATYPUS beamline [53][54][55] at the OPAL reactor at ANSTO, Lucas Heights, Australia. Figure 5 schematically shows the custom-made scattering chamber with FMR capability.…”

Section: In Situ Ferromagnetic Resonance (Fmr) Measurements and Polarmentioning

confidence: 99%

Hydrogen Absorption in Metal Thin Films and Heterostructures Investigated in Situ with Neutron and X-ray Scattering

Callori

Rehm

Causer

et al. 2016

Metals

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Due to hydrogen possessing a relatively large neutron scattering length, hydrogen absorption and desorption behaviors in metal thin films can straightforwardly be investigated by neutron reflectometry. However, to further elucidate the chemical structure of the hydrogen absorbing materials, complementary techniques such as high resolution X-ray reflectometry and diffraction remain important too. Examples of work on such systems include Nb-and Pd-based multilayers, where Nb and Pd both have strong affinity to hydrogen. W/Nb and Fe/Nb multilayers were measured in situ with unpolarized and polarized neutron reflectometry under hydrogen gas charging conditions. The gas-pressure/hydrogen-concentration dependence, the hydrogen-induced macroscopic film swelling as well as the increase in crystal lattice plane distances of the films were determined. Ferromagnetic-Co/Pd multilayers were studied with polarized neutron reflectometry and in situ ferromagnetic resonance measurements to understand the effect of hydrogen absorption on the magnetic properties of the system. This electronic effect enables a novel approach for hydrogen sensing using a magnetic readout scheme.

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“…The Platypus time-of-flight neutron reflectometer was used to perform the neutron reflectometry measurements at the OPAL Reactor at the Australian Nuclear Science and Technology Organisation (ANSTO) [26]. A cold neutron spectrum (2.8 Å < !…”

Section: Neutron Reflectometrymentioning

confidence: 99%

Diffusion of nitroaromatic vapours into fluorescent dendrimer films for explosives detection

Ali¹,

Chen²,

Cavaye³

et al. 2015

Sensors and Actuators B: Chemical

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Abstract:Fluorescence-based sensing with organic semiconductors is a powerful method for the detection of a broad range of analytes including explosives, chemical weapons and drugs.Diffusion of an analyte into an organic semiconductor thin film, and its subsequent interaction with the chromophore are key factors that govern the sensing performance of a chemosensor.In this study the diffusion behaviour of an explosive analyte analogue into a sensing film of a conjugated dendrimer was investigated using a quartz crystal microbalance (QCM) and correlated with neutron reflectivity measurements. The mechanistic insights of paranitrotoluene (pNT) sorption in the films of different thicknesses of a first generation dendrimer with fluorenyl surface groups, carbazole dendrons and a spirobifluorene core were studied and interpreted in terms of the underlying kinetics and thermodynamics. Sorption measurements suggest that the process of diffusion of pNT vapour into the dendrimer films is Super Case II, which involves swelling of the film. Swelling of the film was confirmed by neutron reflectometry measurements, which also showed uniform distribution of the pNT molecules throughout the entire film thickness. The activation energy barrier and change in Gibbs free energy in the sorption process were calculated from the QCM responses. The sorption process was found to be thermodynamically (not kinetically) controlled and independent of film thickness. This work sheds insight into the structure-property relationships that govern the performance of organic semiconductor fluorescence-based chemosensors.

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The multipurpose time-of-flight neutron reflectometer “Platypus” at Australia's OPAL reactor

Cited by 155 publications

References 60 publications

Exchange bias in a nanocrystalline hematite/permalloy thin film investigated with polarized neutron reflectometry

Exchange bias in a nanocrystalline hematite/permalloy thin film investigated with polarized neutron reflectometry

Hydrogen Absorption in Metal Thin Films and Heterostructures Investigated in Situ with Neutron and X-ray Scattering

Diffusion of nitroaromatic vapours into fluorescent dendrimer films for explosives detection

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