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A tool to check whether a symmetry-compensated collinear magnetic material is antiferro- or altermagnetic
by Andriy Smolyanyuk, Libor Šmejkal, Igor I. Mazin
Submission summary
| Authors (as registered SciPost users): | Andriy Smolyanyuk |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2401.08784v1 (pdf) |
| Code repository: | https://github.com/amchecker/amcheck |
| Date submitted: | 2024-01-18 15:44 |
| Submitted by: | Smolyanyuk, Andriy |
| Submitted to: | SciPost Physics Codebases |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approach: | Computational |
Abstract
Altermagnets (AM) is a recently discovered class of collinear magnets that share some properties (anomalous transport, etc) with ferromagnets, some (zero net magnetization) with antiferromagnets, while also exhibiting unique properties (spin-splitting of electronic bands and resulting spin-splitter current). Since the moment compensation in AM is driven by symmetry, it must be possible to identify them by analyzing the crystal structure directly, without computing the electronic structure. Given the significant potential of AM for spintronics, it is very useful to have a tool for such an analysis. This work presents an open-access code implementing such a direct check.
Current status:
Reports on this Submission
Strengths
- Provides a reasonably accessible code which can separate AFM and AM materials, provided that a certain set of assumptions are satisfied
- Clear explanation of fundamental symmetry properties distinguishing AFM and AM materials
Weaknesses
- Neglects spin-orbit interactions, even weak, since spin and space coordinates are considered to be decoupled
- In the case of multiple magnetic ions in the crystal structure, a restriction on the code is that each Wyckoff orbit of magnetic atoms has zero net magnetic moment
Report
Given the recent surge of interest in altermagnetic (AM) materials, this paper provides a timely code which can be used to distinguish antiferromagnet (AFM) materials with a spin-degenerate electron band structure from AM materials which feature a momentum-dependent spin-splitting.
Overall, the paper is well written. The code only appears to be valid under a set of restrictions, such as neglecting spin-orbit interactions. Despite this, I think the paper will be useful to specialists in the field. Before I can recommend it for publication, I would ask the authors to address two minor issues listed below.
Requested changes
(1) At the end of section 2.1, the authors write "Thus, to check if the material
is AM, one needs to confirm the absence of these symmetry operations while confirming that
there is some symmetry followed by a spin-flip that relates up and down sublattices". Everything in this section is clear to me up to this last sentence. It is in particular the part "... ome symmetry followed by a spin-flip that relates up and down sublattices" which is unclear to me. Namely, in a conventional AFM material, the system is invariant under an inversion + a spin-flip. Isn't this precisely the type of operation the authors refer to in the last part of the statement? It looks like the authors are writing that one needs to confirm that e.g. inversion + spin-flip does not leave the system invariant, and then immediately after they write that there should exist an operation (such as inversion) + spin-flip which leaves the system invariant. Please clarify.
(2) In the beginning of section 2.2 and the figure caption of Figure 1, the authors refer to an NiAs structure. Initially, this confused me a bit since the authors in the main write that As atoms are blue in fig 1a whereas Ni atoms are red. But in the actual figure, it is stated that fig 1a shows FeO. It would be helpful for the reader if the authors clarify precisely what is meant by an NiAs structure (namely the geometrical structure) whereas the materials they actually consider are different from Ni and As.