Scientists from Skolkovo Institute of Science and Technology (Skoltech) have proposed the occurrence of antichiral ferromagnetism, a non-trivial property of certain magnetic crystals that paves the way for a range of new magnetic phenomena.
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This study was performed in collaboration with the KTH Royal Institute of Technology, and Uppsala University. The study was published in the Physical Review B journal.
The so-called chirality, or handedness, is considered to be a highly significant basic property of objects in various fields of mathematics, physics, chemistry and biology. It is not possible to superimpose a chiral object on its mirror image by any means. Human hands are the simplest chiral objects, and hence the term itself. The opposite of chiral is called achiral: a circle or a square are normal achiral objects.
It is possible to apply chirality to much more complicated entities, for example, opposing internal interactions in a magnetic system can result in the formation of periodic magnetic textures in the structure that vary from their mirror images. This is known as chiral ferromagnetic ordering.
Chiral crystals are broadly regarded as promising candidates for magnetic data storage and processing device realization as data can be encoded through their non-trivial magnetic textures.
Anastasia Pervishko, research scientist at the Skoltech Center for Computational and Data-Intensive Science and Engineering (CDISE), along with her collaborators utilized symmetry-based analysis and numerical computations to predict the occurrence of antichiral ferromagnetism — a type of ferromagnetic ordering when both forms of chirality (handedness) exist at the same time and interchange in space.
In contrast to chiral and achiral textures, we predict a fundamentally different magnetic ordering in tetrahedral ferromagnets. We use the term ‘antichirality’ to highlight the spontaneous modulation of magnetization direction with a spatial chirality alternation between right- and left-handedness induced by crystal symmetry.
Anastasia Pervishko, Research Scientist, Center for Computational and Data-Intensive Science and Engineering, Skolkovo Institute of Science and Technology
Pervishko notes that the chirality in this periodic magnetic texture alternates in space while the average torsion invariant remains zero.
One can picture it as a magnetic modulation where some part is characterized by right-handedness and the other by left-handedness; that differs drastically from conventional chiral textures where handedness is preserved.
Anastasia Pervishko, Research Scientist, Center for Computational and Data-Intensive Science and Engineering, Skolkovo Institute of Science and Technology
The researchers demonstrated that antichiral ferromagnetism can be found in a group of crystals in which several minerals are naturally formed. To perform this, magnetic ordering in the structure with tetrahedral crystal symmetry was studied and micromagnetic analysis was used to infer this new antichiral ordering.
Thanks to this unconventional ground state, the proposed magnetic ordering might result in a rich family of magnetic phenomena including unique magnetic domains and skyrmions that are fundamentally different from chiral textures. This finding triggers further theoretical and experimental investigation in this type of magnetic materials.
Anastasia Pervishko, Research Scientist, Center for Computational and Data-Intensive Science and Engineering, Skolkovo Institute of Science and Technology
The study was performed with funding from the Russian Foundation for Basic Research Project No. 19-32-60020 and the Russian Federation President Scholarship.
Journal Reference:
Rybakov, F. N., et al. (2021) Antichiral ferromagnetism. Physical Review B. doi.org/10.1103/PhysRevB.104.L020406.