Effect of substrate misorientation on domain stretch velocities in chevron expanders

Substrate misorientation of an epitaxial garnet film induces an in-plane anisotropy, which in turn causes a domain wall velocity anisotropy. We have measured velocity anisotropies in weakly and moderately misoriented films using a high speed optical sampling microscope. The in-plane anisotropy axis determined from bubble radial expansion measurements agrees reasonably well with theory. Subsequently, we have measured domain stretch velocities in two orthogonal chevron expanders fabricated on the misoriented films with one expander nearly parallel and the other nearly perpendicular to the in-plane easy axis. It is found that domain stretch velocities are indeed anisotropic with the velocity difference in two orthogonal stretch directions nearly equal to that between the two anisotropic saturation velocities in the bubble radial expansion measurements. However, the domain stretch velocities themselves are much larger than the radial saturation velocities. This discrepancy may be attributed to the presence of an in-plane field in the device.