Abstract
The iron-containing crystals of the langasite family are a new class of multiferroics in which ferroelectricity can be induced by magnetic ordering. We have measured Mössbauer spectra of a powder sample of this family in a wide temperature range and developed a physico-mathematical model for analyzing the complex Mössbauer spectra shape. This model allows establishing a helical magnetic structure at all temperatures in the magnetic ordering region . It is shown that the experimental Mössbauer spectra are well described by the model of a helical magnetic structure with a constant angle of rotation of the moment (rotation step) during its transfer between adjacent planes. The angle value is about 51°, which agrees with the previous results of neutron experiments. The excited states of the magnetic moments that appear at finite (nonzero) temperatures are also taken into account, which makes it possible to study the magnetic dynamics at different temperatures. The value of the angle between the main axis of the electric field gradient (EFG) at the iron nuclei and the crystal axis , which does not change with the temperature in the region , is established. This indicates that in the region of magnetic ordering of this langasite no structural transitions occur. The developed model promotes a deeper understanding of the magnetic properties of the multiferroic and can be used to study the magnetic structure of other compounds where iron ions form a similar helical structure.
- Received 15 August 2018
DOI:https://doi.org/10.1103/PhysRevB.98.134434
©2018 American Physical Society