  We have studied ferromagnetic Permalloy clusters obtained by
electrodeposition on n-type silicon. Magnetization measurements reveal
hysteresis loops almost independent on temperature and very similar in shape to
those obtained in nanodisks with diameter bigger than 150nm. The spin
configuration for the ground state, obtained by micromagnetic simulation, shows
topological vortices with random chirality and polarization. This behaviour in
the small diameter clusters (~80nm), is attributed to the Dzyaloshinskii-Moriya
interaction that arises in its hemispherical geometries. This magnetization
behaviour can be utilized to explain the magnetoresistance measured with
magnetic field in plane and out of sample plane.
