We investigate the existence and origin of magneto-optical anisotropy in epitaxial hcp Co films. Our results show that a significant magneto-optical anisotropy exists in our samples and, more importantly, they reveal that its amplitude is directly correlated with epitaxial strain. We find a linear coefficient of $16.8\%$ magneto-optical anisotropy per every 1% epitaxial strain, which is in stark contrast to an isotropic magneto-optical coupling factor $Q$, a very frequent and common assumption in magneto-optics of metallic thin films and multilayers. In addition, the Co films exhibit a similar strain-induced increase of the magnetocrystalline anisotropy energy, evidencing the fact that both magneto-optical anisotropy and magnetocrystalline anisotropy are dependent on the modification of the spin-orbit coupling introduced by anisotropic lattice distortions.

• Received 14 February 2014
• Revised 9 September 2015

DOI:https://doi.org/10.1103/PhysRevB.92.184405