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Charge imbalanced layered 4f-magnet GdAl2Ge2
by Dmitry V. Averyanov, Ivan S. Sokolov, Oleg E. Parfenov, Alexander N. Taldenkov, Oleg A. Kondratev, Andrey M. Tokmachev, Vyacheslav G. Storchak
Submission summary
| Authors (as registered SciPost users): | Vyacheslav Storchak |
| Submission information | |
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| Preprint Link: | scipost_202403_00035v1 (pdf) |
| Date submitted: | 2024-03-25 18:34 |
| Submitted by: | Storchak, Vyacheslav |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approach: | Experimental |
Abstract
Layered f-magnets make a prolific source of unconventional quantum phases and functional properties. Recently, a class of Zintl materials EuA2X2 has emerged as holding promise for ideal Weyl and axion physics. The question is whether the magnetic structure, strongly coupled to the topology, can be controlled in such materials via a minimal yet selective modification of their chemical composition. Here, we report qualitative changes in the magnetic structure due to charge imbalance. Such imbalance is probed by replacement of Eu with Gd. The two elements form isoelectronic 4f^7 cations but contribute different numbers of electrons. A synthetic route to epitaxial films of GdAl2Ge2 on Ge, employing a self-sacrificial template, is proposed. The atomic and magnetic structures of the films, their electron transport properties are studied by a combination of techniques. It is established that the change in the magnetic structure caused by the cationic replacement influences the magnetotransport properties of the films. The results suggest that the charge imbalance in Zintl compounds may provide an instrument to open new routes to functional layered materials with potential applications in spintronics.
Current status:
Reports on this Submission
Report
Averyanov et al. report the synthesis and characterization of epitaxial thin films of GdAl2Ge2 on Germanium, demonstrating the structural purity and magnetic properties of their films. The manuscript is generally very well written and clear, reads easily and explains the essential details of this work.
The data on which this report is based is a bit limited, however. For example, surface characterization of the films, magnetic phase diagrams, and more detailed comparison to the bulk data is required for publication.
If AI software was used to ‘clean grammar mistakes’, please indicate this in the Acknowledgements.
Requested changes
I will recommend publication after changes as follows:
1. Please construct a magnetic phase diagram (including dependence on film thickness) and compare to the result for bulk samples, if available.
2. Please show a Curie-Weiss plot of your film’s magnetization data (MT curve). Please compare the CW temperature of the film to the bulk sample. Does the CW temperature show any anisotropy?
3. Please provide more characterization of the films, especially AFM and TEM measurements so the quality of the surface and the deposition can be determined.
4. Can you please explain more clearly why the intermediate GdGe2 layer helps in the epitaxial process, although its lattice mismatch is not much better, as compared to GdAl2Ge2, than Ge(111)? There is some comment in the present version, but I found it not so clear and hard to understand for laypeople.
5. EuAl2Ge2 and GdAl2Ge2 exist as bulk materials, so it would be possible to discuss their charge-transfer behavior and magnetic properties using bulk crystals. The manuscript does not very clearly state the advantage of doing so using thin films. Please make this more clear in the introduction and even the abstract.
6. Can you please plot RT curves for your film as compared to typical bulk samples of EuAl2Ge2 and GdAl2Ge2, maybe as an inset in one of the figures? Are both materials metallic, or is one a semimetal and one a ‘good’ metal?
7. GdAl2Ge2 seems to show a spin-flop transition, while EuAl2Ge2 does not (Fig. 3) Can you comment on this behavior?
8. In Fig. 2a, please label all axes (x, y, z). In Fig. 1, please add labels for the crystal axes.
9. Recently, helimagnetic orders have been investigated in layered structures, such as Nature 602, 601–605 (2022) and arXiv:2306.04854 for rare earth materials. Can the present Zintl compounds give rise to more complex, noncollinear spin textures?