MLZ is a cooperation between:

Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Geesthacht> Helmholtz-Zentrum GeesthachtForschungszentrum Jülich> Forschungszentrum Jülich
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MLZ (eng)

Lichtenbergstr.1
85748 Garching

HEiDi

Single crystal diffractometer on hot source

HEIDI scheme HEIDI scheme

The single crystal diffractometer HEiDi is designed for detailed studies on structural and magnetic properties of single crystals using unpolarized neutrons and Bragg’s Law:

2 dhkl  sin (Θ) = λ

Because of the large variety of short wavelengths and resolutions (figure 1, see gallery) HEiDi is suitable for studies on a lot of crystalline compounds – many of them of potential interest for energy or data storage technologies – like:

  • HT superconductors (e.g. cuprates, FeAs-pnictides)
  • Multiferroics (e.g. manganites) and other complex ferro- and antiferromagnetic compounds (e.g. Co-olivines)
  • Ionic conductors (e.g. nickelates)
  • Ferrolelectrica (e.g. KDP family)
  • Mixed crystals (e.g. AsSe compounds)
  • Highly absorpbing compounds (e.g. with Gd, Sm, Eu)
Typical Applications

In general

  • Structure analysis
  • Hydrogen bonds
  • Static and dynamic disorder
  • Harmonic and anharmonic mean square displacements
  • Twinning
  • Magnetic structure and order
  • Spin densities
  • Structural and magnetic phase transitions
  • Incommensurate structures

In detail

  • Studies of atomic positions and bond distances in compounds with heavy and light elements or elements of similar electron shells
  • Temperature dependent studies for determination of phase transitions
  • Studies of order-disorder phase transitions, e.g. H bonds by determination of anisotropic mean square displacements using large Q range up to sin(Θ)/λ > 1
  • Structure determination of compounds with hiqhly absorbing elements (Gd, Sm, Cd) with short wavelengths
  • Studies on magetic phase transitions and T dependencies (ferri, ferro and antiferro magnets, multiferroics)
  • Studies on HT superconductors (e.g. cuprates, FeAs pnictides)
  • Sample characterization by profile analysis
  • Determination of sample orientation, e.g. for preparation of experiments on triple axes instruments
  • Presentation of fundamentals of crystallography and structure analysis for education

Sample Environment
  • Closed cycle cryostat (2 K – RT)
  • Mirror furnace (RT – 2000 K)
  • Micro furnace (RT – 500 K)
  • Uniaxial pressure cell (from PUMA)
Technical Data

Beam-tube

SR9B (hot source)
Flux at sample 1.4·107 cm-1s-1 (λ ≈ 1.17 Å)
Gain by hot source × 10 (λ ≈ 0.6 Å)

Wavelength

2ΘMGe(311)Cu(220)Ge(422)Cu(420)
20°0.5030.4430.4080.280
40°1.1680.8700.7930.552
50°1.4431.0790.9930.680

Q-range

2ΘMGe(311)Cu(220)Ge(422)Cu(420)
20°1.461.952.123.09
40°0.740.991.091.57
50°0.600.800.871.27

Optical components

  • Single detector optimized for small wavelengths (sensitivity >90% at 0.3 Å)
  • Analyzer PG(002); optional for studies of purely elastic scattering and background suppression
  • Neutron filters for suppression of λ/2- or λ/3 contamination of the monochromatized beam

Instrument Scientists

Dr. Martin Meven
Phone: +49.(0)89.289.14727
E-Mail:

Dr. Andrew Sazonov
Phone: +49.(0)89.289.11764
E-Mail:

HEIDI
Phone: +49.(0)89.289.14828

Operated by

Logo RWTH_AIXTal

Gallery

FWHM
FWHM

Figure 1: FWHM of reflections from a Si sample measured with a wavelength of 0.87 Å using the Cu (220) monochromator.

HEIDI
HEIDI

MLZ is a cooperation between:

Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Geesthacht> Helmholtz-Zentrum GeesthachtForschungszentrum Jülich> Forschungszentrum Jülich