SUBSTRATE-TEMPERATURE EFFECT ON THE STRUCTURAL ANISOTROPY IN AMORPHOUS TB-FE FILMS

Using extended x-ray absorption fine structures (EXAFS) measurements w e have investigated the atomic environment around the Fe atom in a ser ies of amorphous Tb0.26Fe0.74 films having different magnetic anisotro py energies owing to different deposition temperatures. The polarizati on properties of synchrotron radiation allowed the separate study of s tructure parallel and perpendicular to the sample plane. An anisotropy between these two structures was observed. Modeling results indicate this anisotropy is due to anisotropic pair correlations where the Fe-F e pairs are statistically preferred in-plane and the Fe-Tb pairs out-o f-plane. The amplitude of this anisotropy scales with both the substra te temperature and the magnetic anisotropy energy. A almost-equal-to 1 % in-plane compression of the Fe-Fe distance was measured between the in-plane and out-of-plane structure of the sample grown at 77 K. This sample had no detectable local chemical anisotropy suggesting that int rinsic stress plays an important role in determining its magnetic anis otropy.