Magnetic anisotropy of (100)- and (110)-oriented epitaxial CrO2 films grown on SnO2- the effects of strain and interface

The crystal structures and magnetic properties of CrO2 films of different orientations and thicknesses grown on SnO2 were investigated and compared with those on TiO2. Results reveal that large anisotropic strains were found in (100) films, but only small strains existed in (110) films. The magnetic anisotropies of CrO2 (110) films on SnO2 and TiO2 were found to be similar. As for CrO2 (100) films, magnetic anisotropies were quite different-at the same thickness, the magnetic anisotropy of the film on SnO2 substrate was higher than that on TiO2. However, the easy axes of the films were found to be always along c axis even at very small thickness, and no easy axis switching was observed. First-principle calculations reveal that magnetic anisotropy energy is not only concerned with anisotropic strain but also with the substrate. The competition between the anisotropic preference of interface and the effect of strains may be one important factor for determining the actual easy axis direction. The combined effects of strain and interface may also be one reason for the magnetic anisotropic difference between CrO2 (100) films on SnO2 and TiO2.