Retrieving the Intrinsic Microwave Permittivity and Permeability of Ni-Zn Ferrites

Round 1

Reviewer 1 Report

The authors have investigated “Retrieving the Intrinsic Microwave Permittivity and Permeability of Ni-Zn Ferrites ”. The main finding is ‘The experimental evidence for the difference between dielectric and magnetic mixing rules for composites’ and, the magnetic domain is a possible origin behind this. The article can be accepted for publication after addressing the following questionnaire.

1.     Authors have considered various possibilities for the discrepancy. What is the calculated density of the studied Ni-Zn ferrites? Usually, this can vary widely depending on the sample synthesis. Why they did not consider the density of the sample for the discrepancy?                                                                                                                                                  

2.     In the SEM image, the scale bar should be given properly for better visibility. The typical particle size varies from 2 um to 20 um which is found from SEM measurements. Since the magnetic domain can be a possible origin of the discrepancy, what could be a typical domain size of Ni-Zn ferrite? I believe that it should be less than particle size. The size of the domain should be discussed in the manuscript.

 

 

Comments for author File: Comments.pdf

One example: In page 7, 'The values of static permeability differ by two orders of magnitude. Although the permeability of the composite is perfectly described by the mixing rule.' It should be a single sentence.

Author Response

The authors are grateful to the reviewers for the useful comments. We made our best to amend the paper promptly. The revisions in the manuscript are marked by green to simplify comparison with the original version.

1. The density of the ferrite bulk is found from the volume and mass of the sample and is 5.0 g/cm3. The found density coincides with the typical values for NiZn ferrites.

We assume that the powder has the same density as the bulk ferrite. Densities may vary for example due to the presence of air pores in the bulk ferrite sample. This leads to an error in the determination of the volume concentration and consequently in the calculation of intrinsic properties. However, these errors cannot lead to a discrepancy in the permeability by two orders of magnitude.

We have added this consideration to the manuscript.

2. We have changed the scale of SEM images for better visibility of the particle size.

The typical size of domains in NiZn ferrites is 1-4 µm [1,38,39]. Stone-like particles are quite strongly distributed in size and among them should be present both single-domain and multi-domain particles.

We have added a discussion of domain sizes on page 11-12.

We studied the manuscript more carefully and corrected typos and errors.

Author Response File: Author Response.pdf

Reviewer 2 Report

In this MS, The normalized inverse susceptibility approach is applied to analyze the microwave properties of composite materials filled with Ni-Zn ferrite powder. The applicability of the mixing rules to permittivity and permeability and the possibility of retrieving the intrinsic properties of inclusions are studied. The experimental evidence for the difference between dielectric and magnetic mixing rules for composites is obtained in this MS. Although the experimental work is sound, the abstract, discussion, and conclusion parts need to be improved before publication in Coatings. 

1. The difference between the mixing rules for permittivity and permeability was previously predicted only theoretically. The experimental evidence for difference between dielectric and magnetic mixing rules for composites is obtained in this paper.

2. For the material Ni_0.32Zn_0.68Fe₂O₄. Additional characterization data such as PXRD, XPS etc. can be provided. I checked the reference 26. There is no standard method or characterization provided except for the SEM analysis.

3. the conclusion part, abstract and discussion need improvement in terms of telling the outcome of the experimental observation.

4. The Figure components can be provide for the figures 3, 4, 5, 7, 8 and 9.

No Comments

Author Response

The authors are grateful to the reviewers for the useful comments. We made our best to amend the paper promptly. The revisions in the manuscript are marked by green to simplify comparison with the original version.

1. We have corrected this phrase to avoid repetition.

The experimental evidence for difference between dielectric and magnetic mixing rules for composites, which was previously predicted only theoretically, is obtained. 

2. We have added EDX analysis data to confirm the correctness of the chemical composition.

For our study, a more important role is played not by the possibility of applying the material under study, but by checking the correctness of using mixing rules. Therefore, we focused our attention on the measururing and analysing dielectric and magnetic properties of ferrites.

3. We have finalized the conclusions, abstract and discussion by adding a discussion of the results obtained and comparing them with existing theories.

4. We have added the data of these figures to the Supplementary Materials.

Author Response File: Author Response.pdf

Reviewer 3 Report

When submitting the amended version of this work, certain critical aspects deserve to be addressed, including the following:

1.      It is important that the originality of this work be brought out in the open throughout the updated text.

2.      What are the advantages and disadvantages for using the microwave?

3.      What is the importance of inserting Table and equations into the introduction part which is not regular to be utilized in the scientific papers? I prefer the introduction part does not contain any of those items. If it is necessary the authors maybe added to the experimental part.

4.      It is strongly suggested that the authors elaborate on the primary rationale for the choice of the ferrite type (Ni-Zn Ferrites and their associated derivatives) that were utilized in this investigation. Why not use some other type of ferrite formulations?

5.      The abstract section is good, unfortunately, it does not contain any numerical results, therefore, it is recommended to add such numerical results which encourage the reader to continue reading the research articles.  

6.      Additional information about the used materials should be added to the experimental sexton under a title chemicals and reagents. This might be included, the purity of the materials and the purchasing company and its location (country and city)  

7.      The authors are highly appreciated to confirm the chemical structures for the synthesized materials. Yes, for sure the SEM images can give evidence but unfortunately more characterizations are required for such preparation before talking about the desired applications. Therefore, for the prepared materials, additionally, XRD studies as well as FTIR analyses can be employed.

8.      Figures 7 and 8 include a significant noise, therefore the authors are appreciated to make curve smoothing for better illustration of the figures. Specially figure 8 which contains higher level of such noise in the lower frequency range.   

9.      The reader would have a better understanding of the information presented in the book if there is a schematic illustration mechanism included in this work, which is highly welcomed.

10.  The conclusion part, it too short and additional results might be added to conclude the work significantly.

 

11.  There are just a few typos and grammatical faults discovered throughout the text; however, the writers are respectfully requested to verify the entire corrected text for any remaining problems.

There are just a few typos and grammatical faults discovered throughout the text; however, the writers are respectfully requested to verify the entire corrected text for any remaining problems.

Author Response

The authors are grateful to the reviewers for the useful comments. We made our best to amend the paper promptly. The revisions in the manuscript are marked by green to simplify comparison with the original version.

1. We have revised the text of the article, revealing the originality of the work more clearly. We have added additional explanations regarding what was done for the first time in our work on pages 2 and 4.

2. Microwave technology is extensively used for telecommunications and radar engineering due to the ease of focusing into narrow beams, wide bandwidth, high data transmissions rates and small antenna sizes.

   For our study, it is important that the permeability of ferrites has a strong frequency dispersion in the microwave range. This makes it possible to evaluate the applicability of mixing rules over a wide frequency range.

   We have described this in the introduction.

3. We removed the table and formulas from the introduction and added them to a separate section "research method". 

4. This ferrite was chosen for research because of the high static permeability and the strong difference in microwave properties between powder and bulk materials. In general, any material with low permittivity and conductivity can be suitable for this study. However, a small difference in the properties of the powder and bulk material could be attributed to measurement inaccuracy.

   The reason for choosing this ferrite is added to the manuscript in the first paragraph of the «Materials  and Methods» section.
5. We have added numerical values of the measured and retrieved static permeability to the abstract.
6. We have added more data about ferrite grade, starting oxides and purchasing company on page 4. We also added EDX analysis data.

7. We have added EDX analysis data to confirm the correctness of the chemical composition.

   For our study, a more important role is played not by the possibility of applying the material under study, but by checking the correctness of using mixing rules. Therefore, we focused our attention on the dielectric and magnetic properties of ferrites.
8. The curves in Figures 8 and 9 have been smoothed.
9. We have added a schematic illustration of the research approach on page 4. 
10. We've added more results to the conclusion part.
11. We studied the manuscript more carefully and corrected typos and errors.

Author Response File: Author Response.pdf

Reviewer 4 Report

SUMMARY

The present manuscript presents an analysis of the possibility of retrieving the intrinsic properties of inclusions, comparison of measured properties of bulk ferrite and properties retrieved by mixing rules from composite materials and study of applicability of the same mixing rule to permittivity and permeability.

 

ORIGINALITY

The present work is original, but we can easily observe from the bibliography that Mr.  Konstantin Rozanov has extensive experience in experimental study of microwave permittivity and permeability of thin metal films (10/34 articles).

 

METHODOLOGY

The methodology used is clearly presented.

 

RESULTS AND INTEREST

The obtained results are notable and I am sure the interest will be high.

 

CONCLUSIONS

This part can be improved by synthesizing the results obtained.

 

REFERENCES Appropriate 

REMARKS:

1.      Research manuscript sections recommended in the Instructions for authors are: Introduction, Materials and Methods, Results, Discussion and Conclusions. I recommend you to respect the sections title of the Coatings Journal and therefore to modify those in your manuscript.

2.      Also, in accordance with the instructions for authors, in the text the consecutive reference numbers should be placed in square brackets [ ]; for example [1–3]. Please modify it in your manuscript.

3.      REFERENCES section:

-        over 76% of the articles cited in the bibliography are older than 5 years;

-        there are a lot of self-citations in this section (≈ 30%).

Author Response

The authors are grateful to the reviewers for the useful comments. We made our best to amend the paper promptly. The revisions in the manuscript are marked by green to simplify comparison with the original version.

We have finalized the «Discussion» and «Conclusions» parts by adding a discussion of the results obtained and comparing them with existing theories.

1. We have changed the titles of the sections in accordance with the recommendations.
2. We have corrected the reference numbers in the paper in accordance with the instructions.
3. We have added more recent articles on the research topic to the bibliography.

 

Author Response File: Author Response.pdf

Reviewer 5 Report

The comments and suggestions for authors are listed in the file attachment. 

Comments for author File: Comments.pdf

Author Response

The authors are grateful to the reviewers for the useful comments. We made our best to amend the paper promptly. The revisions in the manuscript are marked by green to simplify comparison with the original version.

1. μi →1 . We have corrected this typo.

2. We've improved the figures for a better reader experience, and added the concentration insets where possible.

3. The figures have been corrected.

4. Measurements of the permittivity of the bulk ferrite had a high error at frequencies below 10 MHz and above 10 GHz, so these figure is presented in this form.

5. The dependence of the real inverse magnetic susceptibility at a frequency of 0.5 GHz is close to that at a frequency of 1 GHz. We have added this data to the figure and written about it in the manuscript.

6. The real part of the inverse dielectric susceptibility has a linear dependence on concentration, which is typical for the Maxwell-Garnett mixing rule, see Figure 1. However, the imaginary part is not constant and has a systematic concentration dependence that is the same for all observed frequencies. Moreover, the form factor found from the electric inverse susceptibility changes with frequency, see Figure 7, and is different from the form factor obtained from permeability data. Therefore, the MG mixing rule is not applicable to the permittivity.

We have added a more detailed discussion of the difference between the mixing rules for permeability and permittivity in the Discussion part on page 12.

7. Frequency dependences at low frequencies have significant noise due to the peculiarities of measurement and calibration techniques, especially for samples with a low concentra-tion of inclusions. Retrieving the intrinsic permeability from the measured data leads to an additional increase in the noise. Therefore, the curves have been smoothed to better represent the results obtained.

8. The results obtained in the paper may be used in practice for the fabrication of composite materials for microwave absorbers, structured metasurfaces, infrared thin-film absorbers and advanced optical composite materials.

We have added a paragraph with the implementation of the results to practical applications at the end of the Discussion section.

9. Thank you for providing links to the latest works on this topic, we have added them to the paper.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The paper can be accepted in its present form.

Reviewer 5 Report

I thank the authors for their replies, and the replies satisfy me. I would like to recommend the publication of the current manuscript in the journal.