Structure and magnetic properties of RCo/sub 9/Si/sub 2/ systems

RCo/sub 9/Si/sub 2/ alloys (R=Sm, Gd, Tb, and Er) were synthesized and examined by X-ray diffraction and high-field (90 kOe) magnetometry in the temperature range 4.2 to 700 K. X-ray powder diffraction analyses indicated that the major phase crystallizes in the tetragonal BaCd/sub 11/-type structure. The presence of a small amount of extraneous phase was also detected. The magnetic ordering temperatures were observed to vary between 415 and 483 K in order Er, Tb, Gd, and Sm. This behavior is found to follow the de Gennes function and can therefore be ascribed to the strength of the rare-earth-cobalt exchange interaction. The average Co moment in RCo/sub 9/Si/sub 2/ was determined to be nearly 0.9 mu mB at 4.2 K. All compounds studied showed an increase in magnetization with field, beyond technical saturation in fields up to 90 kOe. The M versus T on SmCo/sub 9/Si/sub 2/ indicates a spin reorientation transition at about 60 K. This can be attributed to the effect of the competing anisotropies of the Sm and Co sublattices.<
>