Coexisting Multiple Martensites in Ni57−xMn21+xGa22 Ferromagnetic Shape Memory Alloys: Crystal Structure and Phase Transition
Round 1
Reviewer 1 Report
The submitted manuscript which is entitled “Coexisting multiple martensites in Ni57-XMn21+XGa22 ferromagnetic shape memory alloys: Crystal structure and phase transition” reports experimental results given by high-energy X-ray diffraction, neutron diffraction under applying magnetic fields and high resolution transmission electromicroscopy for Ni57-xMn21+xGa22 in x = 0, 2, 4, 5.5, 7, 8 at.%).
The obtained results clearly show that the structural modulation changes with temperature variation, furthermore, with applying magnetic fields. These findings are valuable in the community of the ferromagnetic shape memory alloys such as related Ni-based Heusler alloy system. The scientific quality is enough to be published in the journal of “metals”. I would like to ask to minor correction before accepting.
1. Introduction
Two paragraphs are related to the topics of the Ni-(Co)-Mn-(In, Sn, Sb) in the Introduction. Because the manuscript basically focuses on the Ni-Mn-Ga alloy, so authors should introduce more previous works on the structural observation and analyses for the Ni-Mn-Ga. In addition, the reason why the present composition was motivated should also be noted.
2. The notation of the series of Ga22-1, Ga22-2,,, rather makes confused. I think the simply, x = 0, x = 2,, would be better.
3. The subscripts in the figures (ex. Figures 3(b)(c), Figure 8(a), Figure 9(a)) are small and unclear, so it is difficult to confirm. I think it is good idea to clarify the difference of the origin of the peak with the colour such as Figure 11.
Below are just comments. Acceptance will not depend the authors will reflect them or not.
I. I am interested in the volume variation with temperature changing. But in the case, the unified unit should be used in the different modulation.
In addition, the crystalline relation between the axes, such as a-axis in austenite phase, root2 of a or c in 7M, a or c in NM should be better shown in sketch.
II. The authors say that “In addition, when the sample was cooled from 380 K to 360 K (310K?), the HEXRD patterns did not show obvious changes in the peak profiles, which unambiguously confirms that there was no structural change associated with the Curie transition.”
It is right. But if the authors will plot the temperature dependence of the lattice parameter or the volume, the spontaneous magnetostrictive change related to the Curie temperature may be appeared.
III. The authors noted that “The magnetic properties were measured in a physical property measurement system (PPMS, Quantum Design) with a magnetic field up to 14 T.” in the session of the Experimental. I am interested in whether the magnetization change would be appeared related to the variation of the structural modulation or not. The change might be small. But if the author analyses it as the magnetic susceptibility in the strong magnetic field, will any changes be seen?
Author Response
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Reviewer 2 Report
This manuscript presents a detailed study of the evolution of the crystal structure as a function of composition and temperature in Ni57-xMn21+xGa22 (x=0, 2, 4, 5.5, 7, 8) magnetic shape memory alloys. Systematic temperature dependent synchrotron X-ray diffraction measurements, complemented by DSC and (not shown) magnetic data allow the authors to establish the phase diagram for this system. A special attention is paid in the manuscript to disentangling the contribution and the evolution of the various martensitic variants. Neutron diffractions and TEM microscopy provide additional support to the results.
Overall this manuscript sounds convincing. It is reasonably well written and presented.
In my opinion, this work should be considered for publication in Metals. I however recommend the authors to consider the following requests for clarifications (calling for minor changes).
1- Is there only one or two thermal events on the DSC measurement of Ga22-3? Please comment whether the 7M – NM transition is associated with any distinguishable enthalpy change. Given that Ga22-3 is a central composition for this study, adding a panel to Figure 1 to present its DSC curve might be considered.
2- Section 3.3, Specify which sample is presented, including in the figure 11 caption.
3- L290-298. Why would the free energy of these multiple martensites become different in magnetic field? Why the free energy of NM martensite is lower than that of 7M martensite in field? This paragraph remains hypothetic and is not really conclusive.
Usually, applying a magnetic field favors the formation of the phase having the highest magnetization. Could the authors compare the magnetization at 100 K of Ga22-1 and Ga22-4?
4- When starting the new paragraph L176, please mention this is the continuation of the description of the same sample, something like: “Fig. 5 shows the HEXRD patterns collected on Ga22-4 upon further cooling from 300 K to 160 K.”
5- L14 “a temperature-dependent in situ synchrotron X-ray diffraction technique” and then in situ is systematically used everywhere in the manuscript. In my opinion this use of a latin word having the primary meaning of “in the original place” (instead of being moved to another place) is abusive. These are temperature dependent synchrotron X-ray diffraction measurements, but on powder specifically crushed for the experiment. We may speak of in situ diffraction measurements when for instance looking inside Li batteries during charge/discharge operations. The qualification “in situ” hardly applies to the present study.
Author Response
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Reviewer 3 Report
The authors present an extensive diffraction and microscopic characterization of different chemical composition of NiMnGa allloys. The aim is to give a complete demonstration of different modulation of martensite and the possiblity to tune among the modulation to have possible perspective of application.
The presence and characterization of 5M, 7M and NM martensite is well presented in literature, but this work is a good resume with specific and interesting experimental results.
The work is well written and presented and I have not particular suggestion to give to the authors. Maybe it is interesting to introduce in the introduction part a comparison and a reference with the paper : V.A. Chernenko, E. Villa, D. Salazar and J.M. Barandiaran, “Large tensile superelasticity from intermartensitic transformations in Ni49Mn28Ga23 single crystal”, Appl. Phys. Lett, 108, Issue 7, 071903 (2016), which is one or maybe the unique example of experimental characterization of the intermartensitic transition in NiMnGa induced by stress.
Author Response
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Reviewer 4 Report
The present study "Coexisting multiple martensites in Ni57-XMn21+XGa22 ferromagnetic shape memory alloys: Crystal structure and phase transition" reports in detail the features of the phase transition between coexisting multiple martensites under external fields and observe the design of novel functional properties based on such phase transitions. This study is well reported and designed. The results are reliable and can be published in present form.
Author Response
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Author Response File: Author Response.pdf
