Effects of adding different types of carbon on the structure and magnetic properties of SmCo6.9Hf0.1 alloy

In this paper, SmCo6.9Hf0.1 as-cast alloys and ribbons with the addition of either graphite (C) or carbon nanotubes (CNTs) were prepared by arc melting and melt-spinning, respectively. The effects of adding carbon on the structure and magnetic properties SmCo6.9Hf0.1 were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), magnetic force microscopy (MFM) and vibrating sample magnetometer (VSM). It was found that the microstructure and magnetic structure of SmCo6.9Hf0.1 ribbons were changed obviously due to the introduction of C or CNTs, although their crystal structure was characterized as the same Sm(Co,Hf)7 single phase, no matter carbon was added or not. As a result, the magnetic properties of carbon-contained ribbons were enhanced in a certain degree. This was considered to be related to the refined equiaxed grains, small domain size and the pinning effect of C or CNTs-rich regions. The magnetic properties of SmCo6.9Hf0.1(CNTs)0.05 ribbons reached Hc=12.5 kOe, Mr=57.0 emu/g and Mr/M2 T=0.788.