Structures and magnetic properties of Co-Zr-B magnets studied by first-principles calculations

Abstract

The structures and magnetic properties of the Co-Zr-B alloys near the Co 5 Zr composition were studied using adaptive genetic algorithm and first-principles calculations to guide further experimental effort on optimizing their magnetic performances. Through extensive structural searches, we constructed the contour maps of the energetics and magnetic moments of the Co-Zr-B magnet alloys as a function of composition. We found that the Co-Zr-B system exhibits the same structural motif as the "Co 11 Zr 2 " polymorphs, which plays a key role in achieving high coercivity. Boron atoms can either substitute selective cobalt atoms or occupy the interstitial sites. First-principles calculation shows that the magnetocrystalline anisotropy energies can be significantly improved through proper boron doping.

Effect of boron doping on nanostructure and magnetism of rapidly quenched Zr2Co11-based alloys

“…This relatively small increase is consistent with Ref. 15 and probably reflects the effect of B on the electronic structure of the host. The amount of Co, estimated from Fig.…”

“…J s decreases with increase in x, mainly because the B suppresses the Co moment. 15 K 1 increases about 15% as the B content increases from x = 0 to x = 3, the change being comparable to the accuracy of the method. The absolute values are somewhat smaller than calculated in Ref.…”

“…3 In particular, boron addition has been found to increase the coercivity of rapidly quenched Zr-Co materials, 13,14 but it is unclear how B addition affects the phase components and structural properties. First-principle calculations 15 are consistent with both B substituting for Co and B occupying "interruption sites" between the motifs. The two occupancies can be distinguished experimentally by considering the unit-cell volume, which increases and decreases for interstitial and substitutional occupancies, respectively.…”

Metastable cobalt nitride structures with high magnetic anisotropy for rare-earth free magnets

“…As a result, there has been a continuing effort in searching for new, RE-free permanent magnets. Many systems have been explored including Fe-Co-(B, N, C), [3][4][5][6] FePt/CoPt, 7 Zr 2 Co 11 , [8][9][10][11] MnBi, 12 and Fe 2 P. 13 Although such studies have led to the improvement of the magnetic properties of the RE-free materials, [14][15][16] the coercivity and energy product of the RE-free magnets are still far below those of RE-magnets. Therefore, continuous efforts in the search for stronger and better RE-free magnets are still highly desirable.…”

Accelerating materials discovery and design: computational study of the structure and properties of materials

“…Chapter 2 introduces the adaptive genetic algorithm developed by us [Wu et al, 2014] to predict atomic structures. Chapter 3 focuses on the applications of our method to the study of non-rare earth magnets, including the Co x Zr polymorphs [Zhao et al, 2014a] and boron-doped Co x Zr alloys [Zhao et al, 2015a]. Meanwhile, the lattice Monte Carlo simulation of the alnico magnet [Nguyen et al, 2015] is also discussed in Chapter 3.…”