Computational screening of Fe-Ta hard magnetic phases

Abstract

In this work we perform a systematic calculation of the Fe-Ta phase diagram to discover novel hard magnetic phases. By using structure prediction methods based on evolutionary algorithms, we identify two new energetically stable magnetic structures: a tetragonal Fe 3 Ta (space group 122) and cubic Fe 5 Ta (space group 216) binary phases. The tetragonal structure is estimated to have both high saturation magnetization (µ 0 M s =1.14 T) and magnetocrystalline anisotropy (K 1 =2.17 MJ/m 3 ) suitable for permanent magnet applications. The highthroughput screening of magneto-crystalline anisotropy also reveals two low energy metastable hard magnetic phases: Fe 5 Ta 2 (space group 156) and Fe 6 Ta (space group 194), that may exhibit intrinsic magnetic properties comparable to SmCo 5 and Nd 2 Fe 14 B, respectively.

Data-driven design of a new class of rare-earth free permanent magnets

“…To determine the origin of the difference in MAE values we analyzed the spin-orbit coupling energy (SOC) of the Co and Mn atoms with their spins oriented along the z and x directions as well as the partial density of states (DOS), similar to the analyses presented in Refs. [46][47][48][49][50][51]. The details of that investigation can be found in Appendix D. Summarizing the results, we find that apart from the Co 3 Mn 2 Ge compound that is listed in the ICSD database, Co 3 Mn 2 Al and Co 3 Mn 2 Ga are also expected to have the properties of a good permanent magnet.…”

“…The later include high magnetocrystalline anisotropy alloys (MnBi [4,5] and MnAl [6,7]), nanostructures [8][9][10][11], thin films [12,13], alnico permanent magnets, and many more [14][15][16][17]. Techniques used for this search include both filtering through a large number of systems [18][19][20][21] and investigating a single or a group of similar compounds [14,15,[22][23][24][25][26][27][28][29]. In Ref.…”

High-throughput design of magnetic materials

“…For instance, within the NOVAMAG project, the evolutionary algorithm has been applied to predict novel permanent materials, leading to Fe 3 Ta and Fe 5 Ta as promising candidates. 61 To summarize, HTP calculations can be performed to validate the stability of known compounds and to predict possible new compounds. The pending challenges are (a) how to systematically address the stability and metastability, ideally with phase diagrams optimized incorporating existing experimental data, (b) how to extent to the multicomponent cases with chemical disorder and thus entropic free energy, so that the stability of high entropy alloys 62 is accessible, and (c) how to perform proper evaluation of the thermodynamic stability for correlated RE compounds and transition metal oxides.…”

“…There have been well established methods as implemented in USPEX [56] and CALYPSO [57] to predict possible crystal structures. For instance, within the NOVAMAG project, the evolutionary algorithm has been applied to predict novel permanent materials, leading to Fe 3 Ta and Fe 5 Ta as promising candidates [58].…”

Origin of phase stability in Fe with long-period stacking order as an intermediate phase in cyclic $γ$-$ε$ martensitic transformation

“…Fe-rich Fe-Mn alloys with hcp structure (ǫ phase) shows the Néel temperature of 230 K. 30 ǫ-Fe-X alloys (X = Ru, and Os) have AFM ground states at ambient pressure with Néel temperatures of ∼100 K. Fe 2 Ta alloy exhibits a paramagnetic state in which either an excess of Fe or Ta can induce ferromagnetic ordering at low temperatures (∼150 K). 31,32 Iron hydride FeH with a double hcp (dhcp) structure exhibit a ferromagnetic ground state under pressure. [33][34][35] On the other hand, no internal magnetic field has been detected for hcp Fe-Ni alloy, even at 11 K under 21 GPa.…”