Structural and compositional inhomogeneities in Bismuth-Substituted rare earth iron garnet epitaxial films

Structural and compositional inhomogeneities in the free-standing epitaxial films of rare earth iron garnet films are characterized using high-resolution X-ray diffraction and energy dispersive X-ray fluorescence. These analyses show a variation in the lattice parameters as well as in chemical compositions, displaying inconsistency from the top and the bottom of the film, suggesting an inhomogeneous distribution of rare earth content. With these variations, intricate changes often occur in the magneto-optics properties. While with conventional X-ray diffraction techniques, the films appeared to be free of gross defects, our high-resolution rocking curves reveal variations in defect density and multiple lattice parameters. These results suggest that epitaxial films presumed to be homogeneous based on conventional X-ray diffractometry, may not be so. Therefore, films found to exhibit exotic physical properties should be carefully examined for the presence of structural and compositional anomalies to optimize the magneto-optic response. If such defects are present, the experimental results may be compromised due to sample imperfections, rather than intrinsic phenomena.