Magnetic properties, phase evolution, and structure of melt spun SmCo7-xNbx (x=0-0.6) ribbons

The phase evolution, microstructure, and magnetic properties of melt spun SmCo7-xNbx (x=0-0.6) ribbons have been investigated using powder x-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer, respectively. SmCo7-xNbx ribbons could crystallize in TbCu7-type structure only for low Nb substitution of x=0-0.3 at high wheel speed of 30-40 m/s. According to the structure refinement, the doping element Nb prefers to occupy the 2e site. The intrinsic coercivity increases dramatically from 1.9 kOe for SmCo7 ribbon to 10.2 kOe for SmCo6.8Nb0.2 ribbon at wheel speed of 40 m/s. The mechanism of the coercivity enhancement has been discussed. The optimal magnetic properties of sigma(r)=54.4 emu/g and H-i(c)=10.2 kOe were obtained in SmCo6.8Nb0.2 ribbon. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3067856]