Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 62: Disodered Magnetic Materials

MA 62.1: Talk

Friday, March 20, 2020, 09:30–09:45, HSZ 401

An ab initio study of magnetism in disordered Fe-Al alloys with thermal antiphase boundaries — •Martin Friák¹, Miroslav Golian¹, David Holec², Nikola Koutná³, and Mojmír Šob¹ — ¹Institute of Physics of Materials, Czech Academy of Sciences, Brno, Czech Republic — ²Department of Materials Science, Montanuniversität Leoben, Leoben, Austria — ³Institute of Materials Science and Technology, TU Wien, Vienna, Austria

We have performed a quantum-mechanical study of a disordered B2 phase of Fe₇₀Al₃₀ alloy with and without antiphase boundaries (APBs) with the {001} crystallographic orientation of APB interfaces. We used a supercell approach with the atoms distributed according to the special quasi-random structure (SQS) concept. Our study was motivated by experimental findings by Murakami et al. (Nature Comm. 5 (2014) 4123) who reported significantly higher magnetic flux density from A2-phase interlayers at the thermally-induced APBs in Fe₇₀Al₃₀ and suggested that the ferromagnetism is stabilized by the disorder in the A2 phase. Our computational study confirms this suggestion (Friák et al. (2019), submitted to Nanomaterials) and explains details of the underlying mechanism. The Fe atoms in the A2 phase have the average magnetic moment by 17.5 % higher than in the B2 phase. We link the changes in the magnetism to the fact that the Al atoms in the first nearest neighbor shell of Fe atoms nonlinearly reduce their magnetic moments (M. Friák and J. Neugebauer, Intermetallics 18 (2010) 1316). Lastly, our atomistic simulations of sharp APBs confirmed a temperature-dependent formation of the A2-phase interlayers.