Arrays of cylindrical permalloy dots of diameter varying from 88 to 20
0 nm were fabricated using high-resolution X-ray and electron beam lit
hography techniques. Reduction of the diameter induces a drastic modif
ication of the magnetisation reversal process. For single domain dots,
interdot dipolar coupling plays an important role for the global stab
le state. Magnetic forte microscopy and alternating gradient magnetome
try results are presented and discussed.