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| Home > Publications database > Setup for polarized neutron diffraction using a novel high-Tc superconducting magnet at instrument POLI at MLZ |
| Home > Publications database > Setup for polarized neutron diffraction using a novel high-Tc superconducting magnet at instrument POLI at MLZ |
| Poster (After Call) | FZJ-2019-00326 |
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2018
Abstract: Polarized neutron diffraction (PND) is a powerful method to investigate magnetic structures. PND can be used for very precise magnetization measurements even for weak magnetic contributions. It allows the high-quality determination of magnetic form factors, to untangle complex (e.g. chiral) magnetic structures, and to follow the movement of magnetic domains. In this technique, spin flip measurements are carried out on a sample, located in a strong magnetic field. Optionally, the scattered beam can be analyzed to perform a polarization analysis along the given field direction at the sample.A new PND setup has been developed for the hot neutron single crystal diffractometer POLI [1] at MLZ. This setup consists of a ³He spin filter cell [2] for polarization, a Mezei flipper optimized for short-wavelength neutrons, and a new high Tc superconducting magnet producing fields up to 2.2 T. Because the magnet provides a symmetric field configuration, a dedicated guide field system was designed in order to avoid neutron depolarization in the zero-field node. The polarization transport efficiency of the whole setup was numerically simulated and optimized [3].By using either a Heusler crystal at the sample position or a second spin filter cell as analyzer, the polarization losses in the setup were confirmed to be below 2% over the total field range of the magnet. With the ³He cell as polarizer, a beam polarization over 90% at a wavelength as short as 0.7 Å is reliably reachable. The stray fields of the magnet did not affect the relaxation time T1 of the ³He spin filter polarizer. Typical T1 values above 100 h are measured. . First experiments with antiferromagnetic and paramagnetic samples using the new setup have been successfully performed. Using the CCSL software, reconstruction of the field induced spin density distribution in the weak ferromagnet MnCO3 was performed in the paramagnetic state and compared to the literature data. Our results shows the high performance and good resolution of the setup.[1] V. Hutanu, Heinz Maier-Leibnitz Zentrum, Journal of large-scale research facilities, 1, A16 (2015)[2] V. Hutanu, M. Meven, S. Masalovich et al., J. Phys.: Conf. Ser., 294, 012012 (2011)[3] H. Thoma, W. Luberstetter, J. Peters, and V. Hutanu, J. Appl. Cryst. 51, 17-26 (2018)
Keyword(s): Instrument and Method Development (1st) ; Magnetic Materials (1st) ; Condensed Matter Physics (2nd) ; Crystallography (2nd) ; Instrument and Method Development (2nd) ; Magnetism (2nd)
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