  Three amorphous Co$_x$Nb$_{100-x}$ alloys, Co$_{25}$Nb$_{75}$,
Co$_{57}$Nb$_{43}$ and Co$_{80}$Nb$_{20}$, were produced by Mechanical Alloying
starting from the elemental powders. Their magnetic properties were determined
using an alternating gradient force magnetometer (AGFM), and the remanent
magnetizations, saturation fields and coercive fields were obtained from the
hysteresis loop. The alloys have a relatively high saturation field, which
decreases as the composition becomes richer in Co. The coercivity and remanent
magnetization reach an optimal value around 57% at.Co, making {\em
a}-Co$_{57}$Nb$_{43}$ the hardest magnetic material among the three alloys.
Further addition of Co produces a soft alloy.
