  Thin films of the ferromagnetic metal SrRuO3 (SRO) show a varying easy
magnetization axis depending on the epitaxial strain and undergo a
metal-to-insulator transition with decreasing film thickness. We have
investigated the magnetic properties of SRO thin films with varying thicknesses
fabricated on SrTiO3(001) substrates by soft x-ray magnetic circular dichroism
(XMCD) at the Ru M2,3 edge. Results have shown that, with decreasing film
thickness, the film changes from ferromagnetic to non-magnetic around
3monolayer thickness, consistent with previous magnetization and
magneto-optical Kerr effect measurements. The orbital magnetic moment
perpendicular to the film was found to be ~ 0.1{\mu}B/Ru atom, and remained
nearly unchanged with decreasing film thickness while the spin magnetic moment
decreases. Mechanism for the formation of the orbital magnetic moment is
discussed based on the electronic structure of the compressively strained SRO
film.
