Magnetic transformation of Mn from anti-ferromagnetism to ferromagnetism in FeCoNiZMnx (Z = Si, Al, Sn, Ge) high entropy alloys

• Published in: Journal of materials science & technology 2021-03, Vol.68, p.124-131
• Main Authors: Zhang, Bin, Duan, Yuping, Zhang, Haifeng, Huang, Shuo, Ma, Guojia, Wang, Tongmin, Dong, Xinglong, Jia, Nan
• Format: Article
• Language: English
• Subjects: Binary alloys; Chemical environment; Crystal structure; Crystallography; Demagnetization energy; Density functional theory; Electron spin state; Entropy; Exchange integral constants; Exchange integrals; Ferromagnetic and anti-ferromagnetic; Ferromagnetic materials; Ferromagnetism; High entropy alloy; High-entropy alloys; Magnetic moment; Magnetic moments; Magnetic state; Magnetic structure; Magnetic transformation; Magnetic transformations; Manganese; Saturation magnetization; Silicon; Spin dynamics; Synergistic effect; Transmission electron microscopy
• ISSN: 1005-0302; 1941-1162
• DOI: 10.1016/j.jmst.2020.06.040

We design high entropy alloys (HEAs) with different induction elements (Si/Al/Sn). In order to keep the crystal structure invariant and to investigate how the increment in saturation magnetization (Ms) is caused only by the change of electron spin state, each set of HEAs contains a different amount of Mn. Synergistic effects among induction elements that induce the magnetic transformation of Mn from anti-ferromagnetism to ferromagnetism are found. Ms of added Mn reduces when a particular induction element (Si0.4/Al0.4/Sn0.4) exists, while a larger increment of Ms appears when two induction elements coexist, Si0.4Al0.4 (25.79 emu/g) and Sn0.4Al0.4 (15.43 emu/g). This is reflected in the microcosmic magnetic structure for the emergence of closed domains due to large demagnetization energy, which is confirmed by the Lorentz transmission electron microscope (LTEM) data. The calculated magnetic moments and the exchange integral constants from density functional theory based on the Exact Muffin-Tin Orbits formalism reveal that the magnetic state and the strength of ferromagnetic and anti-ferromagnetic coupling determine the variation of Ms in different chemical environments. The difference in energy levels of coexisting multiple induction elements also leads to a larger increment of Ms, Si0.4Al0.4Sn0.4 (29.78 emu/g), and Si0.4Al0.4Ge0.4Sn0.4 (31.00 emu/g).