A new Sm(Co,Fe,Cu)4B/Sm2(Co,Fe,Cu)7 cell structure with the coercivity of up to 5.01 T

Highlights: • A new Sm(Co,Fe,Cu)₄B/Sm₂(Co,Fe,Cu)₇ cell structure was obtained. • The microstructural models of the as-spun and annealed ribbons were drawn. • The change in atomic structure before and after annealing was analyzed by EXAFS. • The coercivity was quantitatively analyzed by domain wall pinning mechanism. • The coercivity at 0 K is estimated by low temperature magnetic hardening effect. A new Sm(Co,Fe,Cu)₄B/Sm₂(Co,Fe,Cu)₇ cell structure is found, and its phase composition, microstructure and magnetic properties are investigated. Particularly, the atom structure of main phase is analyzed by extended X-ray absorption fine structure. It was found that as-spun SmCo_2.94FeCu_0.06B ribbons were composed of amorphous phase and approximate equiaxed Sm(Co,Fe,Cu)₄B nanocrystallines. The high disorder of the nanocrystallines leads to the low magnetic anisotropy. After the as-spun ribbons were annealed at 800 °C for 30 min, the amorphous phase disappeared completely. The short rod-shaped Sm(Co,Fe,Cu)₄B grains have a staggered distribution accompanied by ∼8 vol% lamellar Sm₂(Co,Fe,Cu)₇ phase at grain boundaries, and the new cell/cell-wall-type Sm(Co,Fe,Cu)₄B/Sm₂(Co,Fe,Cu)₇ microstructure is produced. The annealed ribbons show an ultra-high coercivity of up to 5.01 T at room temperature, 40.64 T at 5 K (obtained by extrapolating), and estimated to be ∼ 41.96 T at 0 K. The microstructureal models of both ribbons are created and the coercivity mechanism is discussed in detail.