Magnetic properties and microstructure of melt spun YCo5-xMx ribbons (M = C and Sn; x = 0–0.3)

Highlights: • C or Sn doping significantly enhances coercivtiy of melt spun YCo₅ ribbons. • Coercivity enhancement is related to phase constitution and microstructure. • C or Sn entered into the crystal structure of 1:5 phase modifies lattice constants. • C or Sn doping refines the microstructure. • Y₅Sn₃ precipitates with 10–20 nm in diameter appears for YCo_4.7Sn_0.3 ribbon. The doping effects of C and Sn on the magnetic properties, structure, and microstructure of melt spun YCo_5-xM_x (M = C and Sn; x = 0–0.3) ribbons are studied. The permanent magnetic properties of B_r = 5.7 kG, _iH_c = 1.8 kOe, and (BH)_max = 2.1 MGOe are obtained for the binary YCo₅ ribbon, and they are largely increased to B_r = 5.6–5.7 kG, _iH_c = 7.0–14.7 kOe, (BH)_max = 5.3–6.5 MGOe for C-doping ribbons and B_r = 5.5–5.6 kG, _iH_c = 5.2–14.4 kOe, (BH)_max = 3.8–6.2 MGOe for Sn-doping ribbons, respectively. All studied ribbons mainly consist of hexagonal 1:5 phase with space group of P6/mmm. The entrance of C or Sn into the crystal structure of 1:5 phase modifies lattice constants and increases Curie temperature. The microstructure is effectively refined from 100 to 300 nm for binary ribbons to 10–50 nm for C-doping and 60–100 nm for Sn-doping ribbons, respectively. For high Sn-content YCo_4.7Sn_0.3 ribbon, Y₅Sn₃ precipitates with 10–20 nm in diameter form in the matrix, and these nonmagnetic phase may act as a pinning site to impede magnetization reversal and thus contribute to enhance coercivity. Magnetic property enhancement with C-doping is attributed to the formation of Y(Co, C)₅ phase and microstructure refinement, while one with Sn-doping is related to the formation of Y(Co, Sn)₅ phase, microstructure refinement, and the induction of nonmagnetic Y₅Sn₃ precipitates.