  Using focused-electron-beam-induced deposition, Cobalt magnetic nanospheres
with diameter ranging between 100 nm and 300 nm are grown at the tip of
ultra-soft cantilevers. By monitoring the mechanical resonance frequency of the
cantilever as a function of the applied magnetic field, the hysteresis curve of
these individual nanospheres are measured. This enables to evaluate their
saturation magnetization, found to be around 430 emu/cm^3 independently of the
size of the particle, and to infer that the magnetic vortex state is the
equilibrium configuration of these nanospheres at remanence.
