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Polarized neutron diffraction using a novel high‐ T c superconducting magnet on the single‐crystal diffractometer POLI at MLZ
Author(s) -
Thoma Henrik,
Luberstetter Wolfgang,
Peters Jürgen,
Hutanu Vladimir
Publication year - 2018
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s160057671800078x
Subject(s) - diffractometer , neutron , neutron diffraction , magnet , polarization (electrochemistry) , physics , polarizer , optics , neutron scattering , magnetic field , superconducting magnet , materials science , condensed matter physics , diffraction , nuclear physics , superconductivity , chemistry , scanning electron microscope , birefringence , quantum mechanics
The polarized single‐crystal diffractometer POLI is the first neutron scattering instrument routinely using 3 He spin filters both to produce and to analyse neutron polarization. The instrument, with a non‐magnetic goniometer, was designed to perform two types of polarized neutron diffraction experiment: spherical neutron polarimetry, also known as full three‐dimensional polarization analysis in zero magnetic field, and classical polarized neutron diffraction, also called the flipping‐ratio (FR) method, in high applied magnetic fields. Reported here is the implementation of the FR setup for short‐wavelength neutrons on POLI using a new high‐ T c superconducting magnet with a maximal field of 2.2 T. The complete setup consists of a 3 He polarizer, a nutator, a Mezei‐type flipper, guide fields and dedicated pole pieces, together with the magnet. Each component, as well as the whole setup, was numerically simulated, optimized, built and finally successfully tested under real experimental conditions on POLI. The measured polarized neutron spin transport efficiency is about 99% at different wavelengths, e.g. as short as 0.7 Å, and up to the maximal available field of the magnet. No further depolarization of the 3 He cells due to stray fields of the magnet occurs. The additional use of the available 3 He analyser allows uniaxial polarization analysis experiments in fields up to 1.2 T. The results of the first experiment on the field‐dependent distribution of the trigonal antiferromagnetic domains in haematite (α‐Fe 2 O 3 ) are presented and compared with the literature data.