Thursday 11 July 2013, Strathblane & Cromdale Halls, 16:30-18:30
Poster session C - Geosciences and extreme conditions II: Magnetism
P.087 Neutron focusing within sample environment
M Bartkowiak1, U Filges1, T Panzner1, M Forster1 and P Böni2
1
Paul Scherrer Institut, Switzerland, 2Technische Universität München, Germany
The study of novel phenomena in materials science is continuously pushing the sample environment to the
technical limits. For example, very high magnetic fields and high pressures can usually only be achieved by
sacrificing sample volume. Therefore, sample sizes in the sub-mm range have become common practice. In
addition, homogeneous single crystals can often only be grown in a very small size, which is sufficient for most bulk
measurement techniques and for x-ray studies with synchrotron radiation. However, using the flux limited neutron
scattering techniques, small samples lead to a decreased count rate and an accompanied decrease in the signal to
noise ratio resulting in an unrealistically long measurement time or renders the experiment even impossible. Modern
focusing techniques for neutrons can provide a way to surpass these problems by both increasing the number of
neutrons hitting the sample and reducing the background as only the sample is illuminated. We will present novel
neutron transmission measurements using a setup consisting of a pressure cell combined with an integrated
focusing element and a detached prefocusing neutron lens.
P.088 Neutron and X-ray tomography of inclusions in the chondrite meteorite Allende
H H Carlsen1, S S Duchnik1, M Lanczky1, L S Schmidt1, M Thomsen1, M Poulsen2, S A F Lund1, P K Willendrup3, B
Vinter1, C Grünzweig4, D Mannes4, M B Madsen1, R Feidenhans'l1, M Strobl5, H Haack1 and K Lefmann1
1
University of Copenhagen, Denmark, 2Novo Nordisk, Denmark, 3Technical University of Denmark, Denmark, 4PSI,
Switzerland, 5ESS, Sweden
Chondritic meteorites contain samples of the very first solids that formed in our Solar System. Some of these solids
are mm to cm sized particles that formed as individual particles in free orbit around the Sun. Thus, each particle
contains unique information about the birth of our Solar System. Today, we find the particles embedded in fine
grained material in chondritic meteorites. Traditionally, the interior of such rocks have been investigated by cutting
them into thin slices. In many cases the cutting process has destroyed unique inclusions and there is therefore a
great demand for techniques that can identify and locate interesting inclusions before any further processing of the
meteorite. Here, we employ the non-destructive method of tomography, which has the additional advantage that it
may simultaneously reveal the structure and composition of inclusions in the meteorite.
By combined X-ray and neutron tomography, we were able to idenfity and quantize a number of known mm to submm inclusion types of one piece of the often studied chondrite meteorite Allende. Our findings included chondrules,
calcium-aluminum-rich inclusions (CAI's), and metal-mineral grains. Our findings roughly correspond to the results
of other types of studies on similar pieces of this meteorite. Surprisingly, we found an additional object, 3 mm in
diameter, with a homogeneous core and a strongly X-ray and neutron attenuation shell. While the core may be a
chondrule, the composition of the shell is clearly dissimilar to any other material in the meteorite. We speculate that
the shell is a metal-hydrate, where the hydrogen might originate from adsorbed water-ice, present in the primordial
disk orbiting the young Sun.
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P.089 Novel and extreme sample environment at the Helmholtz-Zentrum Berlin - an overview
K Kiefer1, D Wallacher1, S Gerischer1, N Grimm1, A Sokolowski1, H Ryll2, B Klemke1, R Wahle1, P Smeibidl1 and M
Barrett1
1
Helmholtz-Zentrum Berlin, Germany, 2Universität Regensburg, Germany
For a successful operation of a neutron facility it is of particular importance to provide the scientific users the best
technical and scientific support in order to perform highest impact investigations. The quality of the available
sample environment support is certainly a key aspect for excellent scientific results. Sample environment at the
Helmholtz-Zentrum Berlin is traditionally focused on extreme parameters like low temperatures or high magnetic
fields, combined with a strong user support. Strengthening this expertise, the HZB is presently undertaking the
project to build a high field magnet for neutron scattering.
But in addition, two growing trends in neutron scattering are leading to the situation that the focus of sample
environment is more and more shifted away from just providing standard (or even extreme) parameters. First, the
increasing complexity of some the neutron experiments require the combination of neutron scattering techniques
with complementary in-situ experiments or with in-situ sample preparation. Second, new user communities,
especially in the area of soft matter, biology and solid state chemistry push the development of novel specialized
sample environment which is far from being standardized. In both cases sample environment is becoming a more
important and more complex part of the neutron experiment itself. Sample environment at the HZB does already
support these new developments and will further strengthen its efforts on these areas of research. In this
presentation we will give an overview over our recent developments for standard and extreme sample environments,
in-situ experiments and novel specialized sample environment for soft matter, biology and solid state chemistry.
P.090 Addressing potential complications to neutron PDF studies of intact rocks
J Peterson1, H Nakotte1, K Page2 and J Tencate3
1
New Mexico State University, USA, 2Los Alamos National Labs, USA, 3Los Alamos Nation Labs, USA
Neutron pair distribution function (PDF) studies were conducted on a set of intact sandstone and coarsely ground
quartz samples. Unexpected complications were found to arise during the analysis due to large grain sizes. The
desire to conduct the experiments without crushing the sandstone left crystal mosaics big enough to induce
dynamical scattering effects. Existing PDF analysis software is not currently capable of modeling dynamical effects.
We offer workarounds for modelling the neutron dynamical scattering effect in our sample using existing modelling
techniques.
P.091 The synthesis, crystal and magnetic structure of the iron selenide BaFe2Se3
E Pomjakushina1, A Krzton-Maziopa2, V Pomjakushin1, D Sheptyakov3, D Chernyshov3, V Svitlyk4, V Dmitriev3 and K
Conder1
1
Paul Scherrer Institute, Switzerland, 2Warsaw University of Technology, Poland, 3Swiss–Norwegian Beam Lines at
ESRF, France, 4Institut für Anorganische und Analytische Chemie, WWU Münster, Germany
We report on the synthesis of single crystals of BaFe2Se3 and study their crystal and magnetic structures by means
of neutron powder and synchrotron single-crystal x-ray diffraction. The crystal structure has orthorhombic symmetry
(Pnma, CsAg2I3-type structure) and consists of double chains of FeSe4 edge connected tetrahedra intercalated with
barium. Below 240 K, long range spin-block checkerboard antiferromagnetic order is developed. The magnetic
structure is similar to one observed in A0.8Fe1.6Se2 (A = K, Rb or Cs) superconductors. The crystals exhibit a transition
to the diamagnetic state with an onset transition temperature of Tc ~ 11 K [1].
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We have observed a pressure-dependent structural transition in BaFe2Se3 to the CsCu2Cl3-type structure (Cmcm
space group) around 60 kbar, as evidenced from pressure-dependent synchrotron powder diffraction data.
Temperature-dependent synchrotron powder diffraction data indicate an evolution of the room-temperature
BaFe2Se3 structure towards a high symmetry CsCu2Cl3 form upon heating. Around 425 K BaFe2Se3 undergoes a
reversible, first order isostructural transition, that is supported by the differential scanning calorimetry data. On
further heating, a second order phase transformation into the Cmcmstructure is observed at 660 K [2].
[1]
[2]
A. Krzton-Maziopa, E. Pomjakushina, V. Pomjakushin, D. Sheptyakov, D. Chernyshov, V. Svitlyk and K.
Conder.J. Phys.: Condens. Matter 23 (2011) 402201.
Svitlyk V., Chernyshov D., Pomjakushina E., Krzton-Maziopa A, Conder K., Pomjakushin V., Pöttgen R.,
Dmitriev V. arXiv:1301.0509 (2013).
P.092 Extreme environment diffractometer now and in future
O Prokhnenko, W-D Stein, H-J Bleif, M Bartkowiak, N Stuesser and A Tennant
Helmholtz-Zentrum Berlin, Germany
Extreme Environment Diffractometer (EXED) is a new time-of-flight (tof) diffractometer built at the BERII research
reactor at the Helmholtz-Zentrum Berlin (HZB) and optimized for conducting powder and single crystal experiments
in extreme sample environments, in first place high magnetic fields and (ultra)low temperatures. In near future it will
become a home place for the High Field Magnet (HFM), the most powerful DC magnet in the world for neutron
scattering applications. Already now EXED offers user community diffraction experiments in magnetic fields up to 17
T using HZB superconducting magnets. Being combined with HFM, it will become a unique facility for neutron
scattering in magnetic fields beyond 25 T.
To maximize science output in this field range further extension of instrument capabilities is foreseen. This, first of
all, includes an ability to perform inelastic neutron scattering experiments that constitute a rich area of research in
high magnetic fields. Additionally, elastic scattering at low-Qs is of potential interest with focus on nanostructured
magnetism. These are the main goals of the upgrade program launched at EXED: The existing Diffraction mode of
operation will be supplemented by direct tof Spectroscopy and Small Angle Neutron Scattering (tof-SANS). The
contribution will detail both the current status of the instrument and the proposed multimode concept of EXED and
ways for it realization.
P.093 Magnetism in UNiGa under uniaxial pressure
J Prokleska1, M Misek1, V Sechovsky1, J Kamarad2, B Ouladdiaf3 and M-H Lemee-Cailleau3
1
Charles University, DCMP, Czech Republic, 2Institute of Physics, 3Institut Laue Langevin, France
UNiGa is one of the most thoroughly studied materials in the UTX group of compounds crystallizing in the hexagonal
ZrNiAl type crystal structure. It orders antiferromagnetically with TN 39 K and three more transitions between
different AF phases were observed in zero magnetic field in the temperature range 34–39 K.
All phases are characterized by collinear magnetic structures with uranium magnetic moments alligned parallel to caxis. The magnetic structures are built of basal-plane sheets of ferromagnetically coupled U moments, distinguished
by different stacking of the U layers along the c-axis.
In this work we will present the investigation of the magnetic phase diagram under applied uniaxial strain (along the
c-axis) by the means of bulk (magnetization and electrical resistivity) and microscopic (single crystal diffraction D10 and VIVALDI, ILL) measurements. Short note to the construction and utilization of the used uniaxial pressure
cells [1] will be presented as well.
[1]
J. Kamarad et al., 2008, High Press. Res. 28, 633-639.
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P.094 Design of a variable-pressure cell for neutron studies at cryogenic temperatures
C Ridley1, M Jacobsen1, O Kirichek2 and K Kamenev1
1
University of Edinburgh, UK, 2ISIS Spallation Neutron Source, UK
A device for high pressure neutron diffraction, with the ability to vary sample pressure at low temperature, is
presented. The larger sample volumes necessary for neutron studies, as well as the need to implement the loading
mechanism, mean that more massive pressure cells are often required, lengthening cooling time. Similarly the
larger anvils and gaskets required to pressurise the sample increase the background signal contribution. The design
has been optimised through finite-element modelling so as to reduce the thermal mass of the cell to a minimum,
reducing the time taken to reach sub-Kelvin temperatures. The design of the cell is based on an opposed-anvil
arrangement, whilst the anvil housing is easily adaptable to differing anvil dimensions. In addition to this, the
effects of near sample, scattered beam collimation have been simulated using Monte-Carlo methods. The effects of
interactions between the beam and sample environment are known to contribute to the signal from the sample,
though modelling the background from the immediate vicinity of the sample in a high-pressure cell is not easily
estimated. Multiple scattering has been speculated to contribute to some extent [1], though no such effects have
been observed in the simulations presented in the current study. The interaction between a powder sample
enclosed by a gasket and a neutron beam with wavelengths between 1-15 Å has been simulated, and the resulting
diffraction pattern is presented.
[1]
P.A. Seeger, Nuclear Instruments and Methods in Physics Research A 510 pp.290-299 (2003).
P.095 Extreme conditions instrument concept for the European Spallation Source
W-D Stein2, O Prokhnenko1, L Cussen2, K Lieutenant2 and K Prokes2
1
Helmholtz-Zentrum Berlin, Germany, 2Helmholtz-Zentrum Berlin, Berlin, Germany/ESS Design Update Programme,
Germany
The European Spallation Source (ESS) is going to be the brightest source of neutrons in the world for scientific
research. It will be based on a 5 MW long pulse source of neutrons driven by a superconducting proton linac and
provides similar time-averaged neutron flux as the most powerful research reactors. Long pulse source is a novel
approach to efficient neutron production and current challenges are to multiply the source gain by the
corresponding gains in neutron instrumentation tailored for the given source parameters.
As a part of German in-kind contribution to the ESS Design Update phase, we report on development of concept for
the instrument optimized for conducting experiments in extreme environment conditions, such as high magnetic
fields,high pressures, high and low temperatures and combination of those. Based on general complexity of
experimental set-up and sample environment equipment, restricted angular access and small sample sizes, an
instrument concept that provides elastic and inelastic capabilities in broad Q (< 0.01 - 12 Å-1) and energy (1- 80
meV) ranges is proposed. In this contribution the instrument concept will be detailed in combination with the results
of ray-tracing Monte-Carlo simulations. Possible types of sample environment equipment will be discussed.
P.096 The extreme enviroment diffractometer as a tool for diffraction experiments
W-D Stein and O Prokhnenko
Helmholtz-Zentrum Berlin, Germany
The Extreme Environment Diffractometer (EXED) at Helmholtz Zentrum Berlin (HZB) is a time-of-flight diffractometer
with a bispectral source and flexible detector arrangement. It offers several diffraction techniques for the
investigation of materials of actual interest in sample environments available at HZB. The instrument is designed to
operate optimally for a special sample enviroment: the geometry restricted High Field Magnet (HFM) which is
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supposed to start in 2014 with a field of 25 Tesla. High and medium resolution powder diffraction in typical sample
environment is already in use and small angle scattering will be available soon. The investigation of single
crystalline material was recently shown to be successfully working on EXED and we present first results of single
crystal and powder diffraction studies.
P.097 Neutron diffraction investigation of the quantitative texture analysis of metagabro milonite
S Vratislav1, L Kalvoda1, M Machek2 and M Kucerakova1
1
CTU in Prague, Czech Republic, Faculty of Nuclear Sciences and Physical Engineering, 2CAS, Institute of
Geophysics, Czech Republic
Our study deals with the investigations connecting with the quantitative texture analysis of rocks (the four samples
of metagabro mylonite collected from the eastern part of the metagabbro sheet at the Stare Mesto belt, Bohemia
Massif, Czech Republic) by neutron diffraction. The determination of the preferred orientations could help to give the
answer to the context of texture and heat or deformation processes in the rock structures. Each sample was pressed
in the sphere form with the diameter of the 50 mm and the three principal directions forming a Cartesian coordination system: (RD), (ND) and (TD) were defined. Gabro samples consist the two crystallographic phases:
labradorite (triclinic space group C-1) and amphibolite (monoclinic space group C2/m). Diffraction diagrams were
collected on the neutron diffractometer KSN-2 equipped by the texture goniometer TG-1. The set of the measured
patterns was consisted the 90 sample diffraction vectors for data analysis of the gabro samples. The obtained
diffraction patterns were evaluated using the Rietveld method with implementation of the generalized sphericalharmonics description of the effect of texture on reflection intensities.The orientation distribution function (ODF) spherical harmonic coefficients C(l,m,n) – together with the complete texture parameters were determined by GSAS
and ResMat software package. Final refinements for the gabro samples were done with "none" sample symmetry
and maximum harmonic order L=8.
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