Wish science

Wish schematic diagram

A schematic diagram showing the main components of the Wish diffractometer on ISIS TS-2
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Research you can do with the instrument

High-resolution cold-neutron powder diffraction excels when multiple nearly overlapping Bragg peaks occur at long d-spacing. In this case, sheer flux is not sufficient to extract all the available information, and much better results can be obtained with a high-resolution diffractometer, even at the cost of losing some flux.

Complex magnetic systems are the prime scientific target for high-resolution cold-neutron powder diffractometry. In complex systems, the magnetic structure has a large number of degrees of freedom (typically the three components of the magnetic moment on several inequivalent atoms), and the d-spacing range available to observe Bragg peaks is limited due to fall-off of the magnetic form factor. In addition, magnetic and nuclear Bragg peaks are often nearly overlapping, especially in the case of large incommensurate magnetic structures. When the magnetic structure is relatively simple but a crystallographic pseudo-symmetry is present, powder averaging of the magnetic structure factor for quasi-degenerate reflections may prevent the determination of the direction of the magnetic moments, and high-resolution data are required to solve the structure.

Applications

  • Ionic transition-metal compounds
  • Magnetism in covalent systems
  • Model systems
  • Metallic magnets
  • Magnetic clusters and nanoparticles
  • Magnetism under extreme conditions
  • Large-unit-cell structures
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