Thin films of the ferromagnetic metal ${\mathrm{SrRuO}}_3$ (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 ${\mathrm{SrTiO}}_3$(001) substrates by soft x-ray magnetic circular dichroism at the Ru $M_{2,3}$ edge. Results have shown that, with decreasing film thickness, the film changes from ferromagnetic to nonmagnetic at around 3 monolayer thickness, consistent with previous magnetization and magneto-optical Kerr effect measurements. The orbital magnetic moment perpendicular to the film was found to be $\sim 0.1{\mu }_{\text{B}}/\mathrm{Ru}$, and remained nearly unchanged with decreasing film thickness while the spin magnetic moment decreases. A mechanism for the formation of the orbital magnetic moment is discussed based on the electronic structure of the compressively strained SRO film.

• Received 27 March 2015
• Revised 16 May 2015

DOI:https://doi.org/10.1103/PhysRevB.92.064402