Orbital Magnetic Moments in Strained SrRuO3 Thin Films

We carried out x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) spectroscopy and evaluated orbital magnetic moments in compressively strained tetragonal and tensilely strained monoclinic SrRuO3 epitaxial thin films whose magnetic easy axis directions and behavior of the transverse resistivity differ from each other. We found that regardless of the types of the strain, SrRuO3 films have negative orbital magnetic moments arranged antiparallel to the spin magnetic moments along the magnetic easy axis directions. The magnitudes of the orbital moments for both films are similar: similar to-0.17 mu(B)/Ru at 20K. These observations indicate that the films' structures tie only to the direction of the orbital magnetic moments and consequently determine the magnetic easy axis direction in SrRuO3 through the strong magnetocrystalline effect. This highlights the significance of the orbital magnetic moment as a factor determining of the magnetic anisotropy of this oxide. Our results provide important physical insight into magnetic and magneto-transport properties of SrRuO3.