Intrinsic Properties of Fe-Substituted $L1_{0}$ Magnets

Abstract

First-principle supercell calculations are used to determine how elemental additions, especially Fe additions, modify the magnetization, exchange and anisotropy of -ordered ferromagnets. Calculations are performed using the VASP code and partially involve configurational averaging over site disorder. Three isostructural systems are investigated: Fe-Co-Pt, Mn-Al-Fe, and transition metal-doped Fe-Ni. In all three systems the iron strongly influences the magnetic properties of these compounds, but the specific effect depends on the host. In CoPt(Fe) iron enhances the magnetization, with subtle changes in the magnetic moments that depend on the distribution of the Fe and Co atoms. The addition of Fe to MnAl is detrimental to the magnetization, because it creates antiferromagnetic exchange interactions, but it enhances the magnetic anisotropy. The replacement of 50% of Mn by Fe in enhances the anisotropy from 1.77 to 2.5 . Further, the substitution of light elements such as Ti, V, Cr into -ordered FeNi is shown to substantially reduce the magnetization.

Magnetic properties of Fe-doped MnAl

“…For one Fe atom per supercell, there is only one non-equivalent configuration Figure 1(a). For two Fe atoms per unit cell, there are 7 nonequivalent configurations, as previously analyzed for isostructural Fe-Co-Pt [33]. Figure 1(b) shows one of these configurations, where the defected atoms are nearest neighbors and exhibit a hopping contribution that is not accurately described by the CPA.…”

Magnetic anisotropy — How much is enough for a permanent magnet?

“…Tetragonal carbonstabilized MnAl magnets with energy products of ≈50 kJ m −3 were developed in the 1970s [2]. First-principles calculations confirmed strongly ferromagnetic exchange for the short in-plane Mn-Mn distances [29,30] The material is potentially cheap and light, and could repay further research, especially if a magnetic substitution for Al was found that did not couple antiparallel to the Mn.…”

Phase transformation and magnetic properties of MnAl powders prepared by elemental-doping and salt-assisted ball milling

“…16 sample from ∼633 K to 553 K. 16 However, the first-principle supercell calculations indicate that the T c of Mn 15 FeAl 16 might as high as 718 K, which is much higher than that of MnAl, indicating that the Fe-doping to MnAl might increase the T c of the samples. 17 A much higher T c in MnAlC samples contaminated by Fe was observed by Q. Zeng,et al 7 This is another experimental evidence that Fe doping might increase the T c of MnAl.…”