Prediction of the new efficient permanent magnet SmCoNiFe3

Abstract

Indeed, we find a correlation between the number of transition-metal (TM) 3d electrons and the stability of the hexagonal SmTM 5 (D2 d ) compound (TM = Fe, Co, or Ni), see Fig. 1 where we show results from calculations of formation energies. Notice that increasing the 3d electron count (more Ni) greatly stabilizes the compound. An obvious consequence of this behavior is that one should be able to recover crystal stability of a Sm-Fe alloy by doping with 3d electrons from nickel. We compare the theory with experiments [5,6] that closely reproduce the calculated behavior. Notice that an extrapolation of the experimental heats of formation suggests that an alloy with at least 7.2 3d electrons per TM atom is stable. This is important because SmCoNiFe 3 has about 7.3 3d electrons that is enough to stabilize the magnet. It has also recently been confirmed that the related alloy SmNi 2 Fe 3 , that has about 7.5 3d electrons, exist [7] in agreement with the experimental extrapolation outlined in Fig. 1.In a computational search for a thermodynamically viable compound with the maximum portion of iron atoms we recognize that no more than three iron atoms can be accommodated and those occupy the 3g sites that

Rare-earth/transition-metal magnets at finite temperature: Self-interaction-corrected relativistic density functional theory in the disordered local moment picture

“…Interestingly, a recent neutron diffraction experiment reported even larger local moments in SmCo 5 , which add up to give a resultant magnetization in excess of 12µ B /FU [73]. Studies employing DMFT and open-core calculations have reported smaller Sm total moments of approximately -0.3µ B , which would bring the total SmCo 5 moment closer to 8µ B /FU [49][50][51]. Earlier GGA+U calculations found a much larger total moment of 9.9µ B /FU due to a ferromagnetic alignment of Sm and Co spins.…”

Anisotropy and orbital moment in Sm-Co permanent magnets

“…An obstacle is the very limited equilibrium solubility of Fe in the SmCo 5 phase, which is metastable even without Fe addition. Other additives, such as Ti, Cu, Zr, Nb, and Ni, which were also considered from a very early stage [5,16,17,[18][19][20][21][22][23][24][25][26], often improve coercivity but tend to further reduce the magnetization and can therefore only be used in small amounts. A breakthrough occurred with the recognition that Co doping with Cu enhances the solubility of Fe and eventually leads to the formation of a high-magnetization Sm 2 (Co 1−x Fe x ) 17 phase surrounded by Sm(Co, Cu) 5 grain boundaries [3,16,27,28].…”

“…The practical disadvantage of this approach is the low remanence ratio of these essentially isotropic magnets, which overcompensates the magnetization gain due to iron addition, putting them at a competitive disadvantage compared to sintered Sm 2 Co 17 magnets. In fact, it was recently suggested [26] that the addition of Ni in Fesubstituted SmCo 5 stabilizes the 1:5 structure by adding 3d electrons.…”

First-principles Dzyaloshinskii–Moriya interaction in a non-collinear framework

“…For this terms we have derived an expression in terms of multiple scattering electronic structure theory, see Eq. (19) in the "Methods" section. Having Eq.…”

“…Having Eq. (19), it is easy to identify −2J ij δe i δe j and −2D ij δe i × δe j in Eq. 3with −2J * ij δe i δe j and −2D * ij δe i × δe j , respectively.…”