Reflectance Difference-Magneto Optic Kerr spectroscopy (RD-MOKE) was used to study the morphological and magnetic properties of films of organic magnetic molecules, namely, cobalt tetramethoxyphenylporphyrin (CoTMPP) on Cu(110)-(21)O. The purely morphological contribution to the RD-MOKE spectra was used to extract the dielectric function of the organic molecules. Thick layers of CoTMPP ( 20 to 70 nm ) were used as host material for subsequent Ni cluster growth. To this end, a noble gas layer acts as a buffer layer between the substrate and the deposited Ni atoms which diffuse to form 3D clusters . Ni nanoparticles with different size, shape and spatial distribution were created by varying the buffer layer thickness and Ni coverage. The optical and magnetic properties of the Ni nanoparticles after “soft landing” on the CoTMPP molecular films was studied. By using an embedding organic matrix, we try to tune the interparticle interactions as well as the coupling between the organic molecules and the metal clusters, which, for instance, will affect the superparamagnetic behavior of the nanoparticles. In order to address magnetic phase transitions, the experimental setup was upgraded to measure the magneto-optic susceptibility, directly, and over the whole spectral range from 1.5 to 5 eV.  G. D. Waddill, I. M. Vitomirov, C. M. Aldao and J. H. Weaver. Phys. Rev. Lett., 62, p. 1568 (1989).