Magnetic properties, domain structure, and microstructure of anisotropic SmCo_6.5Zr_0.5 ribbons with C addition

The magnetic properties and the domain structure of anisotropic melt-spun SmCo_6.5Zr_0.5 alloys with C addition was investigated by means of x-ray diffraction (XRD), magnetic measurement, and magnetic force microscopy. The XRD analyses showed that the addition of a few percent of C led to a significant increase in the coercivity and simultaneously affected the characterization of crystalline texture of the ribbons. The easy magnetization c axis changed from parallel to the ribbon plane for SmCo_6.5Zr_0.5 ribbons to normal to the ribbon plane for SmCo_6.5Zr_0.5C_0.25−0.75 ribbons. An optimal coercivity of 0.92 T was obtained for the SmCo_6.5Zr_0.5C_0.5 ribbon spun at 5 m/s. The corresponding remanence measured normal or parallel to the ribbon plane was 7.1 kGs or 3.1 kGs, respectively. The domain structure was studied by magnetic force microscopey. A strip-shaped domain was observed on the surface of the SmCo_6.5Zr_0.5 ribbons and the walls lay straight and parallel. For C-doped ribbons, the domain walls formed a maze domain pattern of grains with c axis normal to the ribbon plane. Scanning electron micrographs showed that a dendrite structure was present in the SmCoZr ribbon surface, and C addition caused the above-mentioned dendrite to diminish.