Combinatorial study of C16 phase high entropy borides with high magnetic anisotropy

High magnetic anisotropy materials are critical in numerous technology sectors. The high entropy composition space offers a vast arena for discovery of novel rare-earth free materials with high magnetic anisotropy; however the disordering effect of entropy tends to favor cubic crystal structures whereas uniaxial crystal structures are ideal for high magnetic anisotropy applications [1]. We demonstrate the realization of single-phase magnetic high entropy films with C16 uniaxial crystal structure and enhanced coercivity through introduction of boron. While binary magnetic transition metal C16 borides exhibit moderate easy-plane anisotropy, flipping of the anisotropy to easy-axis may be achieved through suitable mixing of Fe and Co on the transition metal sublattice of the C16 phase [2]. Using a combinatorial sputtering approach, we have explored the wider high entropy composition space to optimize the anisotropy of the C16 phase by incorporation of additional magnetic 3d transition metals. Significant coercivity increase, more than two-fold, has been observed, compared with binary transition metal borides. These results demonstrate a promising boron-assisted synthesis of strong magnetic anisotropy materials.



References

1. Yeh, J.W., et al., Adv. Eng. Mater., 2004. 6, 299 (2004).

2. Kuz'min, M.D., et al., J. Phys. Condens. Mat., 2014. 26, 064205 (2014).