X-ray investigation on the change of crystallographic orientation in epitaxial permalloy induced by Mo island edges

Epitaxial permalloy thin films were prepared on the sapphire substrates via Mo buffer layer. The structure of epitaxial permalloy film is strongly rel ated to the thickness of the buffer layer. Different preferred orientations has been observed as the thickness of the Mo buffer layer increased from 0 to 20 nm. With the in-plane permalloy[0-11] azimuth always locked on the A l2O3 [0001] direction, the permalloy(Ill) is the preferred orientation in p lane normal direction deposition without Mo layer. The preferred orientatio n changes to (220) when the Mo layer thickness increases to more than 0.4 n m, and shifts to (211) when the Mo thickness is larger 1 nm. The variation of epitaxial orientation is attributed to the stabilization of permalloy on Mo island edges. As the Mo buffer thickness larger than 10 nm, the permall oy film is developed into a fee twin structure with 1D disordered stacking parallel to the underlying Al2O3 [11.20] direction.