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arXiv · 2505.09574

Al$_2$MnCu: A magnetically ordered member of the Heusler alloy family despite having a valence electron count of 24

Soumya Bhowmik·Santanu Pakhira·Renu Choudhary·Ravi Kumar·Rajashri Urkude·Biplab Ghosh·D. Bhattacharyya·Maxim Avdeev·Chandan Mazumdar
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Abstract

The magnetic property of the Heusler alloys can be predicted by the famous Slater-Pauling (S-P) rule, which states the total magnetic moment ($m_t$) of such materials can be expressed as $m _t\,=\,(N_V-24)\,\mu_B/f.u.$, where $N_V$ is the total valence electron count (VEC). Consequently, no Heusler alloys having VEC = 24 are theoretically expected as well as experimentally reported to have any magnetic ordering. Recently, a special class of Heusler alloys with 50\% concentration of $p$-block elements (anti-Heusler) have been identified, although none of such reported compounds belong to the VEC 24 category. Here, we report a new anti-Heusler alloy, Al$_2$MnCu, that undergoes long-range ferromagnetic (FM) ordering with $T_{\rm C}\sim$315 K and a large magnetic moment of $\sim$1.8 $\mu_B$/f.u. despite having VEC 24. A phenomenological model based on molecular orbital hybridization is also proposed to understand the magnetism and unusual deviation from the standard S-P rule.

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Soumya Bhowmik, Santanu Pakhira, Renu Choudhary, Ravi Kumar, Rajashri Urkude, Biplab Ghosh, D. Bhattacharyya, Maxim Avdeev, Chandan Mazumdar. 2025-05-14. Al$_2$MnCu: A magnetically ordered member of the Heusler alloy family despite having a valence electron count of 24. https://doi.org/10.1103/physrevb.111.174417

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