MAGNETIC AMORPHOUS CO-GD POWDERS PREPARED BY MECHANICAL ALLOYING

Amorphous Co1-xGdx powders with x=0.10, 0.15, 0.20 and 0.25 were prepa red by mechanically alloying mixtures of elemental cobalt and gadolini um powders in a laboratory high-energy ball mill. The alloys crystalli ze above 500 degrees C. The magnetic properties of the amorphous powde rs were measured in toroidal samples made by cold pressing the powders . For x less than or equal to 0.15, amorphous Co-Gd is ferromagnetic a t all temperatures. In amorphous Co75Gd25, the net magnetic moment has a minimum near the compensation temperature T-com=50 degrees C, at wh ich the cobalt and gadolinium spins align in opposite directions. The low-temperature magnetic moment of this alloy suggests that, on coolin g, it forms a spin glass with a freezing temperature of 60 K.