An ESR experiment on Ni/Pd nano-particles was performed using high frequency and high magnetic field. As a result, special spin polarization in Pd/Ni nano-particles was observed in the Pd core around Ni, although the molecular orbits are made from eigenfunctions of a 3D-well potential. The spin polarization region forms localized or isolated states in the region with low Ni-concentration, but above a concentration of about 4 at%, coupling between the spin polarized regions around Ni appears. ESR-signals of Ni/Pd particles suggest that not only Ni atoms in the surface layer, but also Pd atoms in the core of the particles contribute to the magnetic polarization. (C) 2001 Elsevier Science B.V. All rights reserved.