Effect of Co/Ni Substituting Fe on Magnetocaloric Properties of Fe-Based Bulk Metallic Glasses

Round 1

Reviewer 1 Report

Comments to the Author

The manuscript is devoted to investigations of structural, magnetic and magnetocalloric properties of Fe_80-xM_xP₁₃C₇ (M = Co, Ni; x = 0, 5 and 10 at.%) bulk metallic glasses. I found the paper  interesting and worthy of publishing. However several things, though, are not clear to me and in my opinion they should be rewritten and better explained.

1) Authors should check the text as there are editorial errors in it.

For example:

• a different font size was used on line 79;
• in line 160 there should be a period instead of a comma;
• in the text of the manuscript there is no mentioned item 23, but it is included in the list of references.

2) Moreover:

a) In the Table 1, the saturation magnetization is given in (emu/g), and in the Figure 3 in (T). The units should be standardized.

b) The insert in Figure 3 should have a scale on the x axis.

c) The sentence on lines 125-128 is incomprehensible

“It is well known that Tc is proportionate to the saturation magnetization and the exchange integral….”

3) The authors do not explain in any way the asymmetric shape of the magnetic entropy change peak. Moreover, for the Fe₇₀Ni₁₀P₁₃C₇ and Fe₇₅Ni₅P₁₃C₇ compositions at lower temperatures there is a second peak. Do you know what it is related to?

4) The sentence: "The ??_???? in this paper was calculated…" seems unnecessary, since the authors above show the formula for determining the RC parameter.

5) The authors write:

“Compared with Fe₈₀P₁₃C₇ BMG, the Fe₇₅Co₅P₁₃C₇ BMG shows smaller Δ?_????.” (line182-183)

but the table 1 shows that all compositions have smaller Δ?_????. Why was only the Fe₇₅Co₅P₁₃C₇ mentioned?

6) All compounds exhibit high magnetic transition temperatures. Perhaps it would be good to mention where they could potentially be used.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The article presents valuable, experimental work on the magnetocaloric effect in rare-earth-free Fe-M-P-C (M = Co, Ni) bulk metallic glasses (BMGs). It is a natural continuation of previous investigations on the analogous BMGs without cobalt and nickel doping. By the systematic change of the dopants’ concentration, the Authors found optimal chemical content in terms of the magnitude of the magnetocaloric effect and the change of the Curie temperature. Unfortunately, the article suffers some shortcomings. That is why I recommend publishing it after a minor but important revision.

Abstract:

Why in the last sentence authors decided to write that their materials can be good candidates for magnetic refrigerants instead of “are good for magnetic refrigerant”. What are the obstacles to their direct applications?  These questions should be discussed in Conclusions in the context of other magnetocaloric materials.

Introduction:

Mentioned feature of “low-corrosion” is not a shortcoming. In the Introduction, it should be clearly stated if the Authors would like to explain first of all the physics of magnetocaloric effect in their materials or they are looking for applicational solutions. In the latter case, it would be necessary first to define target parameter values enabling the practical implementations.

Experiment:

Was the chemical composition of the final alloy verified by any spectroscopic method? Moreover, the XRD is in many cases not sufficient to determine dopant distribution – especially in the case of amorphous alloys. As the atoms being substituted are Fe ones, the dedicated method would be the Mössbauer spectrometry. Authors could mention this question e.g. in the discussion and maybe they schedule that type of measurements in future.

Result and discussion:

At what temperature was measured the hysteresis loops? This should be written in the caption to Fig. 3. Additionally, it should be stressed more directly that Fig. 6 are not experimental curves from any heat measurements but just reconstruction from thermomagnetic data and thermodynamical relations (1,2). The uncertainty of such a numerical procedure should be marked in Fig. 6 as error bars. For what temperature saturation magnetic polarization is given in Fig. 7?

 

Conclusions:

Authors claim that investigated materials could “be a potential candidate for magnetic refrigerants”. This statement is not justified. The high fields (several Tesla) and high temperatures (600K) required for obtaining a large change of anisotropy exclude any reasonable applications. In my opinion, the Authors should be focused on a more microscopic explanation of the physics of the observed phenomena. This could be the main substance of the Conclusions.

Language:

The overall level of English is not bad, but in some places, there are serious grammar errors. Thus the text requires careful lingual revision.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The authors explored the effects of Co/Ni substitution on the magnetocaloric properties of an Fe_80-xM_xP₁₃C₇ (M = Co or Ni) bulk metallic glasses (BMGs). It was reported that the BMG exhibited the maximum magnetic entropy change when x = 5. The research results are well presented, but the manuscript needs to be improved, as discussed below.

1. Please define all variables, such as ∆S_M (line 34).
2. There is a lot of scatter in the X-ray diffraction patterns from Figure 1. It is suggested that the authors smooth the curves to ensure that there are no crystalline peaks in the patterns.
3. There are some grammar errors that should be fixed.
4. Why did the authors not form samples with the same diameter? 
5. Please specify how the X-ray diffraction samples were made. Or did they perform X-ray on the entire rod?
6. Why is the magnetization curve for the Fe₈₀P₁₃C₇ so much greater than the other curves at temperatures below ~550 ^oC? Please discuss this in the text.
7. The authors need to better explain how they approximated the partial derivative in the integrand of Eq. (1) with a difference quotient, as written in Eq. (2). They also need to define the variables from Eq. (2). 

Author Response

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Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.