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Origin of the Low Magnetic Moment in Fe2AlTi: An Ab Initio Study

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FRIAK M. SLÁVIK Anton MIHÁLIKOVÁ Ivana HOLEC D. VŠIANSKÁ Monika ŠOB Mojmír PALM M. NEUGEBAUER J.

Druh Článek v odborném periodiku
Časopis / Zdroj Materials
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
Doi http://dx.doi.org/10.3390/ma11091732
Klíčová slova Fe2AlTi; Fe2TiAl; Heusler; magnetism; ab initio; stability; off-stoichiometry; strain
Popis The intermetallic compound Fe2AlTi (alternatively Fe2TiAl) is an important phase in the ternary Fe-Al-Ti phase diagram. Previous theoretical studies showed a large discrepancy of approximately an order of magnitude between the ab initio computed magnetic moments and the experimentally measured ones. To unravel the source of this discrepancy, we analyze how various mechanisms present in realistic materials such as residual strain effects or deviations from stoichiometry affect magnetism. Since in spin-unconstrained calculations the system always evolves to the spin configuration which represents a local or global minimum in the total energy surface, finite temperature spin effects are not well described. We therefore turn the investigation around and use constrained spin calculations, fixing the global magnetic moment. This approach provides direct insight into local and global energy minima (reflecting metastable and stable spin phases) as well as the curvature of the energy surface, which correlates with the magnetic entropy and thus the magnetic configuration space accessible at finite temperatures. Based on this approach, we show that deviations from stoichiometry have a huge impact on the local magnetic moment and can explain the experimentally observed low magnetic moments.
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