The systems for energy production, conversion, and usage are undergoing radical changes to address challenges related to climate change and humanity's ever-increasing need for energy, as well as sustainability. Among the technologies for green energy conversion, such as wind turbines and electric vehicles, as well as industrial automation, permanent magnets (PM) are vital components [1]. From the available materials, two different classes are dominant: the low cost and low performance hexaferrites and the high cost and high performance rare-earth (RE) based compounds, such as Nd-Fe-B and Sm-Co. This scenario leaves a large magnetic performance gap, opening opportunities to develop new materials, that are preferentially cheap, without critical elements (such as RE) and with good secondary properties, such as corrosion resistance [2-3].

The hexagonal Fe2P-based material system fulfils these requirements; however, the binary compound has a low Curie temperature, making it unsuitable for room temperature applications [4]. Given this constraint, further alloying elements can be used to tune the intrinsic magnetic properties and overcome its limitations. In this work, we employed a composition complex approach, introducing Co and Si to the alloy to investigate phase stability and intrinsic magnetic properties. With this objective, single crystals were synthesized by varying the ratio between the elements to identify promising compositions.

After tuning the composition, attempts were made using the rapid solidification technique (melt spinning) to obtain polycrystalline samples. This aimed to investigate how to convert the intrinsic potential into extrinsic engineering magnetic properties. The melt-spun ribbons, with submicrometer-sized grains, exhibited isotropic magnetic properties with a coercivity of 0.04 T, achieving only 2% of the anisotropy field. This disparity indicates that there is still potential for further improvements to maximize properties in Fe-Co-P-Si alloys and achieve a gap magnet material.

This work has received funding from the European Innovation Council and SMEs Executive Agency (EISMEA) under grant agreement number 101099736 (CoCoMag).

References
[1] O. Gutfleisch, et al., Advanced Materials, 2011, vol. 23, pp. 821-842.
[2] K.P. Skokov, O. Gutfleisch, Scripta Materialia, 2018, vol.154, pp. 289-294.
[3] J.M.D. Coey, Scripta Materialia, 2012, vol. 67 (6), pp. 524-529.
[4] Y. He, et al., Advanced Functional Materials, 2022, vol. 32, 2107513.