Alloying effect on the order–disorder transformation in tetragonal FeNi

• Published in: Scientific reports Vol. 11; no. 1; pp. 5253 - 9
• Main Authors: Tian, Li-Yun, Gutfleisch, Oliver, Eriksson, Olle, Vitos, Levente
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04.03.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301; 639/4077; Alloys; Equilibrium; Humanities and Social Sciences; Investigations; Magnetic properties; Magnetism; Materials science; multidisciplinary; Physics; Science; Science (multidisciplinary); Temperature; Tin; Transition temperatures
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-84482-5

Tetragonal ( L1 0 ) FeNi is a promising material for high-performance rare-earth-free permanent magnets. Pure tetragonal FeNi is very difficult to synthesize due to its low chemical order–disorder transition temperature ( ≈ 593  K), and thus one must consider alternative non-equilibrium processing routes and alloy design strategies that make the formation of tetragonal FeNi feasible. In this paper, we investigate by density functional theory as implemented in the exact muffin-tin orbitals method whether alloying FeNi with a suitable element can have a positive impact on the phase formation and ordering properties while largely maintaining its attractive intrinsic magnetic properties. We find that small amount of non-magnetic (Al and Ti) or magnetic (Cr and Co) elements increase the order–disorder transition temperature. Adding Mo to the Co-doped system further enhances the ordering temperature while the Curie temperature is decreased only by a few degrees. Our results show that alloying is a viable route to stabilizing the ordered tetragonal phase of FeNi.