Sm(Co, Fe, Cu, Zr, C)8.2 ribbons for high-temperature magnets

The effect of carbon substitution for cobalt on the structure and magnetic properties at room and high temperature of melt spun ribbons with composition Sm(Co0.86-xFe0.1Zr0.04Cx)8.2 and Sm(Co0.74-xFe0.1Cu0.12Zr0.04Cx)8.2 (x=0-0.015) has been studied. Arc-melted bulk samples have Th2Ni17-type structure while ribbons have TbCu7-type structure. Average grain size for Cu-free sample with x=0.005 is 23 nm while for Cu-doped samples it varies from 53 to 22 nm when x varies from 0.005 to 0.015, respectively. Coercive as-spun samples have Hc∼2.2-7.8 kOe and reduced remanence mr=Mr/Ms up to 0.74. Ribbons of the Cu-free composition with x=0 and 0.005 and annealed at 750 deg. C for 1 h have TbCu7-type structure with coercivity values 4.9 and 3.0 kOe respectively, while for x=0.01 and 0.015, FCC-Co is the dominant phase. Cu-doped ribbons with x=0.005, after annealing at 750 deg. C for 2 h, are characterized at room temperature by square hysteresis loop with Hc=8.3 kOe, reduced remanence mr=0.75 and (BH)max=6.3 MGOe. Loops at higher temperatures are also square with high mr; for x=0.01 the magnetization is 89 emu/g and the coercive field is 1.8 kOe at 400 deg. C