Magnetocrystalline anisotropy ofFe5PB2and its alloys with Co and5delements: A combined first-principles and experimental study

Abstract

The Fe 5 PB 2 compound offers tunable magnetic properties via the possibility of various combinations of substitutions on the Fe and P-sites. Here, we present a combined computational and experimental study of the magnetic properties of (Fe 1−x Cox) 5 PB 2 . Computationally, we are able to explore the full concentration range, while the real samples were only obtained for 0 ≤ x ≤ 0.7. The calculated magnetic moments, Curie temperatures, and magnetocrystalline anisotropy energies (MAEs) are found to decrease with increasing Co concentration. Co substitution allows for tuning the Curie temperature in a wide range of values, from about six hundred to zero kelvins. As the MAE depends on the electronic structure in the vicinity of Fermi energy, the geometry of the Fermi surface of Fe 5 PB 2 and the k-resolved contributions to the MAE are discussed. Low temperature measurements of an effective anisotropy constant for a series of (Fe 1−x Cox) 5 PB 2 samples determined the highest value of 0.94 MJ m −3 for the terminal Fe 5 PB 2 composition, which then decreases with increasing Co concentration, thus confirming the computational result that Co alloying of Fe 5 PB 2 is not a good strategy to increase the MAE of the system. However, the relativistic version of the fixed spin moment method reveals that a reduction in the magnetic moment of Fe 5 PB 2 , by about 25%, produces a fourfold increase of the MAE. Furthermore, calculations for (Fe 0.95 X 0.05 ) 5 PB 2 (X = 5d element) indicate that 5% doping of Fe 5 PB 2 with W or Re should double the MAE. These are results of high interest for, e.g., permanent magnet applications, where a large MAE is crucial.

Structural transformation and magnetic properties of (Fe$_{0.7}$Co$_{0.3}$)$_2$B alloys doped with 5$d$ elements: A combined first-principles and experimental study

“…Very similar behavior for 5d impurities in Fe matrix has been predicted previously, with the minimum for Os and maximum for Pt [36]. We have also presented similar results for 5d impurities in Fe 5 PB 2 compound [33].…”

“…It has been shown previously, that the growth in the MAE seen for W and Re dopants is primarily due to the strong spin-orbit coupling of 5d element. However, other changes in the electronic structure also have an impact on MAE [11,33]. The calculations from this work predict that the MAE increases from 1.17 MJ m −3 for (Fe 0.7 Co 0.3 ) 2 B to about 2.34 MJ m −3 for (Fe 0.66 Co 0.28 Re 0.06 ) 2 B.…”

Electronic specific heat coefficient and magnetic properties of Y(Fe1−xCox)2 Laves phases: A combined experimental and first

“…−1 . That discrepancy originates, among others, from the limitations of the LDA, which is recognized as an underestimating of magnetic moment [47]. Simultaneously, we used the lattice parameters calculated within the LDA (underestimated by about 0.3Å) [7], which additionally decreased the magnetic moment.…”

Effect of transition metal doping on magnetic hardness of CeFe$_{12}$-based compounds

“…In all cases, we optimized the geometry with a force convergence criterion of 10 −3 eV Å −1 . Similar systematic supercell approach has been previously used to model the (Fe,Co,X) 2 B [26] and (Fe,Co,X) 5 PB 2 alloys [27]. CeFe 12 crystallizes in a tetragonal structure with space group I4/mmm [14,15], see Table I and Fig.…”