Large Uniaxial Magnetic Anisotropy of Hexagonal Fe-Hf-Sb Alloys

Round 1

Reviewer 1 Report

This work studies the effect of doping Sb into Fe2Hf in order to improve its magnetic anisotropy for use as permanent magnetic application. The study combines several first-principles methods, including KKR, FLAPW, and VASP, and is rather extensive. The calculated magnetic moment and anisotropy are in reasonable agreement with experiment. This is a very useful computational work that should be published. There are a couple of minor issues that the authors can address.

1. The authors calculated the enthalpy of formation. For the FeHfSb alloy considered they found -0.724 eV/fu, compared to -1.165 eV/fu for pristine Fe2Hf. Although these are meaningful results, the enthalpy of formation is calculated against elemental Fe, Hf, and Sb crystals. A more relevant comparison is to use Fe2Hf, elemental Sb, and Fe (to account for the excess Fe) because this will tell us whether Sb will intermix with Fe2Hf or segregate. A quick estimate using (-0.724)+(0.5)(-1.165) = -0.142 eV/fu indicates that Sb will not segregate. The authors should mention this.
2. The final analysis using Bruno's perturbation theory can be improved. Bruno's approach was a many-body theory and implemented with a tight-binding Hartree-Fock method. It is not quite suitable for use with DFT calculations. It also lacks the ability to analyze orbital by orbital contribution to anisotropy. A DFT based approach was given by Wang et al, PRB47, 14932 (1993). See also Yang et al, PRB 95, 174424 (2017) for an example of orbital by orbital analysis.

Author Response

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Reviewer 2 Report

Kyvala et al. have studied the electronic structure and magnetic properties of Fe2Hf hexagonal phase. They have shown that substitution of Sb leads to change in magneto-crystalline anisotropy from in-plane to uniaxial phase. This approach can indeed be considered as an alternative approach in processing rare-earth free permanent magnets. The results are presented in coherent way and explained comprehensively. However, I have a couple of ‘minor’ modifications as suggestions before the manuscript can be considered for publication:

1. The authors have cited reference 20 as the description for computational procedure. They should provide a brief explanation of the procedure in the manuscript for better readability and completion of the work.
2. There are a few grammatical and spelling mistakes throughout the manuscript. A thorough proof reading is necessary.

 

Author Response

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