NREX

Neutron reflectometer with X-ray option

N-REX

The high resolution neutron/ X-ray contrast reflectometer NREX, operated by the Max Planck Institute for Solid State Research, is designed for the determination of structural and magnetic properties of surfaces, interfaces, and thin film systems.

The instrument is an angle-dispersive fixed-wavelength machine with a default wavelength of 4.28 Å. A horizontal focussing monochromator gives the possibility to switch between modes “high intensity/ relaxed resolution” and “high resolution/ reduced intensity” and provides a beam especially for small samples (down to 5 × 5 mm² and below). A Beryllium filter attenuates higher order reflections. Transmittance supermirrors m = 3.5 with a polarising efficiency of P = 99% and high efficiency gradient RF field spin flippers are used for a full 4 spin channel polarisation analysis.

The sample is aligned horizontally. By tilting the sample the incident angle is varied. The detector arm can move for GISANS horizontally as well as vertically for specular and diffuse scattering measurements. Neutrons are detected with a 20 x 20 cm² position sensitive or a pencil detector. An X-ray reflectometer can be mounted on the sample table orthogonal to the neutron beam. It allows for the in-situ characterisation of sensitive soft matter samples and neutron/ X-ray contrast variation experiments.

Typical Applications

The instrument provides specular and off-specular reflectometry as well as grazing incidence small angle diffraction both in polarised and non-polarised modes. While the specular reflectivity allows determining the scattering length density profiles (20 – 1500 Å) with nm precession along the surface normal, the off specular reflectivity is sensitive to in-plane-inhomogeneity like roughness, (magnetic) domains, vortices in superconductors- and clusters- in the µm-range. To probe lateral (in-plane) structures in the order of atom distance (down to few Å) at the surface, grazing incidence diffraction is provided.

Sample Environment

A closed cycle crystat (down to 3.5 K) and an electromagnet for fields up to 0.5 T applicable in all three space-directions with restrictions in field strength are provided. Additionally the standard sample environment (magnets up to 7,5 T and ³He inserts for the cryostat down to 50 mK) are available. To the instrument pool belong a cell for investigations at the solid/ liquid interface and a gastight chamber for experiments under defined environmental conditions (arbitrary atmospheres: for example defined relative humidity) at the solid/ air interface.

Technical Data

Monochromator

Type	7 × 5 HOPG crystals
	Horizontal focussing
Wavelength	4.28 Å
Wavelength resolution	1…2%
Distance to sample	2500 mm
Higher order filter	cooled Be

Collimation
Vertical
Slit sizes	0.2 – 6 mm
Divergence	0.05 – 1.4 mrad
Horizontal
Slit	0.2 – 100 mm

Polarisation
Beam polarisation	> 99%
Flipper efficiency	> 99%

Detector
2 pencil detectors	³He
2D area detector	³He wire chamber
Active area	200 × 200 mm²
Lateral resolution	3 mm
Distance to sample	2465 mm

Dynamical- and Q-Range
Specular reflectivity	1 : 1 × 10^-6 (@ 5 × 5 mm² sample and full polarisation)
Q_z	0.005 – 0. 5 Å^-1
δQz (0 < Qz < 0.2 Å-1)	< 0.002 Å^-1

X-rays

Source: Cu-Kα fixed anode (1.54 Å)
Monochromator: Goebel Mirror & Double Ge-Crystal
Detector: 0-dimensional NaI scintillation counter

Instrument Scientists

Dr. Yury Khaydukov
Phone: +49 (0)89 289-14769
E-Mail: Y.Khaydukov@fkf.mpg.de

Dr. Olaf Soltwedel
Phone: +49 (0)89 289-14769
E-Mail: Olaf.Soltwedel@frm2.tum.de

Dr. Thomas Keller
Phone: +49 (0)89 289-12164
E-Mail: T.Keller@fkf.mpg.de

NREX
Phone: +49 (0)89 289-14878

Operated by

Publications

Find the latest publications regarding NREX in our publication database iMPULSE:

impulse.mlz-garching.de

Citation of the instrument

Max-Planck-Institut für Festkörperforschung and Heinz Maier-Leibnitz Zentrum. (2015). NREX: Neutron reflectometer with X-ray option. Journal of large-scale research facilities, 1, A38. http://dx.doi.org/10.17815/jlsrf-1-30

For citation please always include the DOI.

Gallery

NREX

Scattering-Map

Scattering-map of spin-up neutrons from the [Fe(10 nm)/Si(10 nm)]x50-multilayer measured in magnetic field H = 1 kGs applied in-plane of the structure (scheme of the experiment on the up-right inset). Left-bottom inset: specular reflectivities for different spin channels

Left: Reflectivity curves from the periodic heterostructure [La_0.7Sr_0.3MnO₃(2 nm)/SrRuO₃ (8 nm)]x15 measured at T = 3 K (sample surface area 5 x 10 mm²). Right: Model of the spin configuration explaining experimental data. Taken from J.-H. Kim et al. Phys. Rev. B 86, 180402® (2012)

MLZ is a cooperation between:

> Technische Universität München

> Helmholtz-Zentrum Geesthacht

> Forschungszentrum Jülich