Permanent Magnetic Properties of Melt-Spun YCo₅C_x Ribbons

Ribbons of nominal compositions YCo₅C_x (x = 0, 0.2, 0.4, 0.6) are prepared by melt spinning at surface velocities v=5, 10, 15, 20, 25, 30 and 35 m/s. YCo₅ ribbon is crystallized in a single YCo₅ phase of hexagonal CaCu₅ structure. A small quantity of YCoC₂ phase appears in the ribbons with C addition besides the YCo₅ phase. With the increase of x the lattice constant c increases and a along with the unit cell volume decreases. The largest values of _iHc=888 kA/m and (BH)_max =58.4 kJ/m³ at present for the YCo₅ ribbon system were obtained with x=0.4 and v=20 m/s. The improvement of the permanent magnetic properties is rooted in the refinement of the microstructure and the appearance of the YCoC₂ phase which can act as domain wall pinning centers.