Tailoring properties of Heusler alloys by elemental substitution and electron counting: (Co$_{2-α}$Mn$_α$)FeGe, Co$_2$(Fe$_{1-β}$Mn$_β$)Ge, and (Co$_{2-α}$Fe$_α$)MnGe
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866912603646722048 |
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| author | Mahat, R. Budhathoki, S. Regmi, S. Law, J. Y. Franco, V. Butler, W. H. Gupta, A. Hauser, A. LeClair, P. |
| author_facet | Mahat, R. Budhathoki, S. Regmi, S. Law, J. Y. Franco, V. Butler, W. H. Gupta, A. Hauser, A. LeClair, P. |
| contents | Rational material design by elemental substitution is useful in tailoring materials to have desirable properties. Here we consider three non-equivalent substitutional series based on Co$_2$FeGe, viz; (Co$_{2-α}$Mn$_α$)FeGe, Co$_2$(Fe$_{1-β}$Mn$_β$)Ge, (Co$_{2-α}$Fe$_α$)MnGe ($0\!\le\!α\!\le\!2, 0\!\le\!β\!\le\!1$), and study how material properties evolve with the interchange of Mn, Fe, and Co in Co$_2$FeGe. In all three schemes, single-phase compounds can be obtained over a wide range of compositions: $0.125 < α< 1.375 $ for (Co$_{2-α}$Mn$_α$)FeGe, $0 \!\le\! β\!\le\! 1$ for Co$_2$(Fe$_{1-β}$Mn$_β$)Ge, and $0 \!<\! α\!<\! 1.50$ for (Co$_{2-α}$Fe$_α$)MnGe. All the single-phase compounds crystallise in fcc structure with chemical ordering consistent with the ``4-2'' rule of Butler et al. The compounds are soft ferromagnets with low temperature saturation magnetisation agreeing with the Slater-Pauling rule. Very high Curie temperatures are measured, with values up to 1000 K for lower Mn concentrations. First principle calculations indicate, in the most stable atomic configuration, Mn prefers sharing sublattice with Ge, also consistent with the 4-2 rule. The calculations further predict half-metallic behaviour for (Co$_{1.625}$Mn$_{0.375}$)FeGe, while finding other compositions to be nearly half-metallic. Upon comparing the results of the three series, it is found that single-phase alloys occur for a specific range of valence electrons per unit cell ($\sim\!28.5\!-\!29.75$), and that even for multi-phase samples the structural, magnetic, and electronic properties depend primarily on the number of valence electrons and not on the specific substitution scheme employed. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_20546 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Tailoring properties of Heusler alloys by elemental substitution and electron counting: (Co$_{2-α}$Mn$_α$)FeGe, Co$_2$(Fe$_{1-β}$Mn$_β$)Ge, and (Co$_{2-α}$Fe$_α$)MnGe Mahat, R. Budhathoki, S. Regmi, S. Law, J. Y. Franco, V. Butler, W. H. Gupta, A. Hauser, A. LeClair, P. Materials Science Rational material design by elemental substitution is useful in tailoring materials to have desirable properties. Here we consider three non-equivalent substitutional series based on Co$_2$FeGe, viz; (Co$_{2-α}$Mn$_α$)FeGe, Co$_2$(Fe$_{1-β}$Mn$_β$)Ge, (Co$_{2-α}$Fe$_α$)MnGe ($0\!\le\!α\!\le\!2, 0\!\le\!β\!\le\!1$), and study how material properties evolve with the interchange of Mn, Fe, and Co in Co$_2$FeGe. In all three schemes, single-phase compounds can be obtained over a wide range of compositions: $0.125 < α< 1.375 $ for (Co$_{2-α}$Mn$_α$)FeGe, $0 \!\le\! β\!\le\! 1$ for Co$_2$(Fe$_{1-β}$Mn$_β$)Ge, and $0 \!<\! α\!<\! 1.50$ for (Co$_{2-α}$Fe$_α$)MnGe. All the single-phase compounds crystallise in fcc structure with chemical ordering consistent with the ``4-2'' rule of Butler et al. The compounds are soft ferromagnets with low temperature saturation magnetisation agreeing with the Slater-Pauling rule. Very high Curie temperatures are measured, with values up to 1000 K for lower Mn concentrations. First principle calculations indicate, in the most stable atomic configuration, Mn prefers sharing sublattice with Ge, also consistent with the 4-2 rule. The calculations further predict half-metallic behaviour for (Co$_{1.625}$Mn$_{0.375}$)FeGe, while finding other compositions to be nearly half-metallic. Upon comparing the results of the three series, it is found that single-phase alloys occur for a specific range of valence electrons per unit cell ($\sim\!28.5\!-\!29.75$), and that even for multi-phase samples the structural, magnetic, and electronic properties depend primarily on the number of valence electrons and not on the specific substitution scheme employed. |
| title | Tailoring properties of Heusler alloys by elemental substitution and electron counting: (Co$_{2-α}$Mn$_α$)FeGe, Co$_2$(Fe$_{1-β}$Mn$_β$)Ge, and (Co$_{2-α}$Fe$_α$)MnGe |
| topic | Materials Science |
| url | https://arxiv.org/abs/2509.20546 |