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

The doping effects of C and Sn on the magnetic properties, structure, and microstructure of melt spun YCo5-xMx (M = C and Sn; x = 0-0.3) ribbons are studied. The permanent magnetic properties of Br = 5.7 kG, iHc = 1.8 kOe, and (BH)max = 2.1 MGOe are obtained for the binary YCo5 ribbon, and they are largely increased to Br = 5.6-5.7 kG, iHc = 7.0-14.7 kOe, (BH)max = 5.3-6.5 MGOe for C-doping ribbons and Br = 5.5-5.6 kG, iHc = 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 YCo4.7Sn0.3 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.