Work

Rare-earth-free Fe2P-based compounds: Tuning and modeling of hard magnetic properties

Year: 2026

Type: article

Abstract: Fe 2 − x Co x P 1 − y Si y has attracted significant attention for permanent magnet applications due to its promising intrinsic magnetic properties and the absence of strategic elements such as rare earths. To date, most samples reported in the literature are polycrystalline and obtained via mechanical alloying, which makes direct measurement of magnetocrystalline anisotropy particularly challenging. In contrast, only a limited number of single-crystal compositions have been investigated. In this work, Fe 2 − x Co x P 1 − y Si y polycrystalline samples were synthesized by combined induction and arc melting techniques. Compared with mechanically alloyed materials reported in the literature, the resulting samples exhibit a higher degree of phase purity, with secondary phases appearing only in specimens with high Si content. The composition dependence of the intrinsic magnetic properties, namely Curie temperature, saturation magnetization, and magnetocrystalline anisotropy, was systematically investigated over the compositional range 0.1 ≤ x ≤ 0.3 and 0.1 ≤ y ≤ 0.4 , extending beyond the range previously explored in single crystals. The anisotropy field was directly measured on polycrystalline samples by means of the Singular Point Detection technique in pulsed magnetic fields. The maximum anisotropy field μ 0 H A = 2.84 T was found for Fe 1.90 Co 0.10 P 0.80 Si 0.20 , which also exhibits a saturation magnetization M S = 111 A m 2 /kg and a Curie temperature T C = 495 K. All investigated compounds display a magnetic hardness parameter κ > 1 and tunable intrinsic magnetic properties. The theoretical maximum energy product approaches 200 kJ/m comparable to values obtained for single crystals. These characteristics, together with the possibility of obtaining nearly single-phase materials through scalable melting routes, make this compound family one of the most promising candidates for rare-earth-free permanent magnets with performance intermediate between ferrites and rare-earth magnets. Experimental results were complemented by density functional theory calculations, which were used to map the magnetic moment and magnetocrystalline anisotropy energy over a broader compositional space. The calculations reveal that band filling plays a crucial role in optimizing the anisotropy and overall magnetic performance of the Fe 2 − x Co x P 1 − y Si y system.

Source: Acta Materialia

DOI: 10.1016/j.actamat.2026.122802