Effect of Film Thickness on Microstructural and Magnetic Properties of Lithium Ferrite Films Prepared on Strontium Titanate (001) Substrates
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this work, author investigate the effect of film thickness on their microstructure and magnetic properties of lithium ferrite films prepared on SrTiO3 (001) substrates. After going through this manuscript, some statements are unclear and need some revise or amendment.
1. Section (2. Materials and Methods), please Include the type and model of sputtering system used in this work. Include their related deposition parameter (such as target to substrate distance, on-axis or off-axis ad etc.)
2. Section (3. Results and discussion, line 78-94), Give some explanation (such as growing condition and mechanism or any others reason.) that causing the obtain of difference crystal structure or orientation formation.
3. Section (3. Results and discussion, line 90-91), “Instead of forming crystalline orientation domains in the 7.5-nm-thick 90 film, there present some {111} TBs in the 30-nm-thick film.”, Why TBs is not observed in 7.5nm sample? Is it too thin or any other reason. Please explain.
4. Section (3. Results and discussion, line 95-97), “All the parameters are close to…”, Do you have any bulk material results, need to show in this manuscript.
5. Section (3. Results and discussion, line 103-115), Give some explanation (such as growing condition and mechanism or nay others reason.) that causing the obtain of difference microstructure and strain relaxation behaviors.
6. Refer Figure 2.d, What did the blue arrows denote?
7. Section (3. Results and discussion, line 137-138), “In contrast, the formation of a high density of twins…”, cannot see clearly in the TEM image, can denote with an arrow in the figure which part has high density?
8. Section (3. Results and discussion, line 141-142), “Fig. 4a and 4b present the M-H hysteresis…”, Explain why there is difference value obtained between in-plane and out-of-plane value.
9. Figure 4, Suggest adding an enlarge (zoom-in) curve to clearly show the intercept of coercivity and remanence value.
10. Section (3. Results and discussion, line 164-166), “It is considered that the enhanced Ms…”, which result confirm the possibility of oxygen vacancies, suggest verifying via XPS or other suitable method.
Author Response
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Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIn the present manuscript, authors have reported the fabrication of lithium ferrite (LiFe5O8) thin films on strontium titanate (SrTiO3) substrate. The effect of the thickness on the microstructural and magnetic properties of LiFe5O8 thin films has been reported. It was found that the formation of structural defects can be influenced by the thickness of the film. The magnetic measurement shows that the thinner films have enhanced magnetization and a relatively lower coercive field compared with the thicker films containing the antiferromagnetic twin boundaries. The subject is interesting and can be considered for publication after few minor revisions:
1) Authors have used some abbreviations/chemical formulae which are not defined in the text e.g SrTiO3, Fe2O3 etc. Although these are common formulae even then it is advised to define them in the text where they are used for the first time for better understanding.
2) Purities of reagents/chemicals and technical details of the instruments are not mentioned.
3) In figure 4, a & b is not labeled and also visibility of the text in that figure is poor.
4) The results indicated that the 7.5 nm thick film displayed a larger saturation magnetization and a relatively lower coercive field in comparison with the 30 nm thick film. Authors should justify these results in the result and discussion section.
5) References must be updated. There is no reference from 2023 and only one paper is cited from 2022.
Comments on the Quality of English Language
Overall manuscript is well written. Minor editing of English language is required.
Author Response
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Reviewer 3 Report
Comments and Suggestions for AuthorsThe current manuscript investigate the effect of film thickness on microstructural and magnetic properties of lithium ferrite films prepared on SrTiO3 (001) substrates. The interest of the current study is average and can have some interest for researchers who have the same research interest. The manuscript is well-written and describes the outcome data very well. However the presentation of the outcoming result needs to be organized in a better way. Thus, I recommend a major revision for the current version of the manuscript and accept it after fixing these issues:
1- The sample preparation needs to be enhanced with more information about the target preparation. In addition, the thin film fabrication missing a lot of information such as deposition parameters, whether the samples rotate or not, applying a magnetic field to control the magnetic anisotropy of the samples, the distance between the target and the magnetron sputtering, which kind of sputtering technique, RF, DC, AC and so on.
2- How the authors control the layer thickness of the sample and confirm from it.
3- The authors should add an explanation about the selected of annealing conditions 800 C, what about lower or higher this temperature? What about the capping layers, Do the authors use Pt for the capping layer as appeared Pt in Figure 1? This information is mandatory to describe in the revised version of the manuscript.
4- Also, the STEM sample preparation is loosed, I recommend the authors describe in detail the preparation conditions or cite their previous works describing the sample fabrications.
5- The authors said “The magnetic hysteresis 72 (M-H) loops were measured by a SQUID (Quantum Design) with magnetic field applied 73 along STO [100] and [001] directions, respectively.” Can explain in detail how to fix that configuration? Also, “The quartz paddle and brass half-tube 74 were used as sample holders for M-H loops along in-plane (STO [100] direction) and out-75 of-plane (STO [001] direction), respectively.” It will be great if the authors added figures in the supplementary parts to illustrate these magnetic set-up.
6- Please, add references support this point “Considering the four-fold symmetry of the SrTiO3(001) substrate surface, there exists an equivalent OR having a 90° in-plane orientation relation to the latter OR.”
7- Please add more discussion about this observation “Instead of forming crystalline orientation domains in the 7.5-nm-thick 90 film, there present some {111} TBs in the 30-nm-thick film”
8- I recommend the authors add the source and explanation of why they selected this calculation as they said: “In the LiFe5O8/SrTiO3 heterostructure, the lattice mismatch is calculated to be about 130 +6.2% for cube-on-cube epitaxy, using the formula [(af-2as)/2as]*100%.”
9- For the magnetic measurement I recommend the authors add low-scale INP&OOP loops to show the differences between the two samples and add the additional table to extract all magnetic parameters such as Hc, Ms, Mr, Hk, Ku and for both directions with this the readers can see the effect of layer thickness. Also, the calculation of Keff and Keff * t parameters will be very useful for the researchers. The authors can use the same estimations reported in these references (https://iopscience.iop.org/article/10.1088/1361-6528/abb109/meta and https://iopscience.iop.org/article/10.1088/1361-6528/abb109/meta)
10- The conclusion needs to be enhanced with the possible application of depending on the magnetic and structural behaviour and add the future investigation related to the outcome results.
Author Response
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Reviewer 4 Report
Comments and Suggestions for AuthorsReview remarks and recommendations for manuscript Coatings-2747831 entitled “Effect of film thickness on microstructural and magnetic properties of lithium ferrite films prepared on SrTiO3 (001) substrates”.
The presented study is focused on the structural and very basic magnetic (hysteresis) properties of LiFe5O8 / SrTiO3 thin films prepared by magnetron sputtering – comparative view of two samples with different thickness – specifically resulted in different level of structural disorder. The study is directed in perspective direction based on the LiFe5O8 versatility. However, the analysis it is a bit limited in a key aspects and I would suggest to the authors to improve the discussion level with further major revision of the manuscript.
Remarks:
- Please distinguish better between the previously presented TEM analysis in Journal of Materials Science & Technology 40 (2020) 31–38, what is the difference between the 30 nm sample in JMST compared to the similar/identical ~30 nm sample in the currently submitted text?
- There is a straightforward note that “… Thus, the most likely factor responsible for the thickness-dependent magnetic properties is the strain state and the microstructure of the film.” Natural conclusion, but this is only under the current magnetron deposition parameters and this definitely should be emphasized in the text. The observed tendency may change with broad parameters variation experiments (different substrate temperature for instance). Important comparison can be done with this (missing) reference Applied Physics A (2019) 125:566 - https://doi.org/10.1007/s00339-019-2850-z and PLD.
- In a similar context, the presented experimental details concerning the sputtering process are too limited. Please expand with type RF/DC, power, pulse duration etc.. The paragraph is very similar to the previous article in Journal of Materials Science & Technology 40 (2020) 31–38
- Poor presentation of the hysteresis graphs. Please, insert corresponding insets with observable magnification of hysteresis width for coercivity estimation (0 Oe vicinity)
- The DC magnetometric procedure details should be expanded significantly. Considering the emu/cc usage, presumably the size, shape of the thin film samples (disks, plates, irregular) has to be noted altogether with demagnetization factors (especially in this field geometries).
Author Response
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Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors correctly fixed most of my comments. I feel the current version of the manuscript is good for publication in the present form.
Reviewer 4 Report
Comments and Suggestions for Authors
