Dec 8 – 10, 2020 Online only
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Europe/Berlin timezone

The Absolute Direction of the Dzyaloshinskii-Moriya Interaction in Hematite Determined by Polarized Neutron Diffraction

Dec 9, 2020, 2:30 PM
3h 30m
Online event

Online event

Speaker

Mr Henrik Thoma (Jülich Centre for Neutron Science JCNS at MLZ)

Description

Polarized neutron diffraction (PND) is a powerful method which provides direct access to the scattering contribution from nuclear-magnetic interference and thus reveals the phase difference between the nuclear and magnetic structure. This technique can be utilized to gain a detailed insight in the microscopic spin ordering at the unit cell level even for complex magnetic structures. Since magnetic domains correspond to an overall phase shift between the nuclear and magnetic structure, PND also allows to resolve different magnetic domain configurations providing additional information at the mesoscopic scale. This qualifies PND as a versatile tool to simultaneously address a wide range of scientific issues. By conducting a detailed PND study of the prototypical room-temperature weak ferromagnet α-Fe$_2$O$_3$ (hematite) we could solve the long standing problem of inconsistent asymmetry signs observed within Friedel pairs in hematite. Moreover, using a detailed symmetry analysis the absolute direction of the Dzyaloshinskii-Moriya interaction (DMI) vector in α-Fe$_2$O$_3$ could be determined for the first time. This study is supported by a detailed refinement of the slightly canted magnetic structure and by numerical calculations. It can be used as a reference for further DMI sign determinations, reducing the experimental efforts to the measurement of one representative reflection, making it well suited for highly topical materials often requiring extreme sample environment.

Primary author

Mr Henrik Thoma (Jülich Centre for Neutron Science JCNS at MLZ)

Co-authors

Dr Vladimir Hutanu (Institute of Crystallography, RWTH Aachen and Jülich Centre for Neutron Science JCNS at MLZ) Prof. Manuel Angst (Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, Forschungszentrum Jülich GmbH) Prof. Georg Roth (Institute of Crystallography, RWTH Aachen)

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