Microstructure Features of Yttrium Orthoferrite Thin Films on Sapphire

X-ray diffraction and electron microscopy were used to examine the crystal structure features of ultrathin (3-50 nm) yttrium orthoferrite films, obtained by magnetron sputtering of stoichiometric composition target on alpha-Al2O3 substrates with orientation. The morphology and crystal structure of the films differ significantly depending on their thickness. In the thinnest films, several phases are formed, including yttrium orthoferrite with an orthorhombic crystal lattice (o-YFeO3), yttrium hexaferrite with a hexagonal crystal lattice (h-YFeO3), iron-yttrium garnet (Y3Fe5O12), and iron oxides such as hematite and maghemite. The study examines the local composition and determines the orientation ratios between the crystallized phases and the substrate. The films with a thickness greater than 10 nm predominantly exhibit a highly textured phase of o-YFeO3 with a small admixture of iron-yttrium garnet.