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Zeeman term for the Neel vector in a two sublattice antiferromagnet
by Sayak Dasgupta and Ji Zou
|As Contributors:||Sayak Dasgupta · Ji Zou|
|Date submitted:||2021-04-01 06:26|
|Submitted by:||Dasgupta, Sayak|
|Submitted to:||SciPost Physics|
We investigate the dynamics of solitons in two sublattice antiferromagnets under external perturbations, focusing on the effect of Dzyaloshinsky-Moriya (DM) interactions. To this end, we construct a micromagnetic field theory for the antiferromagnet in the presence of the external magnetic field, DM interaction, and adiabatic spin-transfer torque. In particular, we show that the DM vector and external magnetic field can be combined to form a Zeeman field for the Neel vector. We also study perturbations, like strains which can modify (externally) the inertia of the Neel vector field.
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Anonymous Report 1 on 2021-4-11 Invited Report
1- The result positioned as the central achievement of the paper is certainly already known for 35 years.
2- The rest is difficult to evaluate as the paper does not make a sufficiently clear distinction between new/own results and old results, with at least some old results lacking proper references.
I certainly cannot recommend publication in the present form.
The central result of the paper, presented in Eq. (36), the presence of the "Zeeman term" (d,n,h) proportional to the mixed product of the DM vector d, external magnetic fileld h, and the Neel vector n, is known for more than 35 years. One can see that term in Eq. (1.6) in the well-known review "Dynamics of domain walls in weak ferromagnets" by V. G. Bar'yakhtar, B. A. Ivanov, and M. V. Chetkin, Usp. Fiz. Nauk vol.146, pp.417-458 (1985) [English translation: Sov. Phys. Usp. vol.28 , pp. 563-588 (1985)] ; in fact, this term is crucial for the theory of the forced motion of domain walls in weak ferromagnets, presented in Section 3 of the above-mentioned review. [I attach the pdf of the review].
Moreover, the paper, as well as the above-mentioned review of 1985, only present the case of fully antisymmetric DM tensor (when the DMI can be expressed via the DM vector). There is some amount of work devoted to the motion of magnetic solitons in the case of a general DMI [see the review by Ivanov and Galkina, Low Temp. Physics 44, 618 (2018) https://doi.org/10.1063/1.5041427]
If one "subtracts" the above result on the "Zeeman term", it is not clear to me whether the rest is sufficiently novel to warrant publication as an original paper. The problem is, the paper does not make a sufficiently clear distinction between new and old results. For instance, at the end of Sect. IIIA, Eqs (24), (26) show that time-dependent magnetic field leads to a force acting on a domain wall. There is no reference, so one is naturally led to think this belongs to the authors. However, this result has been obtained by Bar'yakhtar, lvanov, Lapchenko, and L'vov, see Fiz. Nizk. Temp. vol.13, 551-553 (1987) [English translation: Sov.J.LowTemp.Phys. vol 13, pp. 312-313 (1987)] and the effect has been first observed by Takuya Satoh et al, Phys Rev Lett vol 105, 077402 (2010). Although from the first paragraph of Sect. IV of the present manuscript the alert reader might indeed suspect that this point is not a new result, the lack of proper citation in Sect. III is misleading.
The large part of the paper, namely entire Sections II and III, seem to be just a review of the literature - if there is any original contribution in there, it is .
In view of the above, I think the text has to undergo a major rewrite before any further discussion can take place.
1- Analyze the literature and provide proper references to the results that are known.
2- Revise the entire text, making a clear distinction between own/new results and the results of other researchers.