A study of magnetic and electronic hyperfine interactions in epitaxial film of yttrium-iron garnet by the method of conversion electron Mössbauer spectroscopy

Magnetic and electric hyperfine interactions in the near-surface layers of epitaxial films of yttrium-iron garnet of the (111) orientation grown by the liquid-phase epitaxy method are studied by the method of the conversion electron Mössbauer spectroscopy (CEMS). The studies reveal a stoichiometric violation of the anion sublattice in the near-surface layers (≈8 × 10–8 m) of yttrium iron garnet film and, as a consequence, the formation of two types of d-sites, which is associated with a significant concentration of point defects in the anion sublattice of the near-surface area and the growing weight of the covalent bonding in the transition film–air layer. This also causes the presence of a fixed doublet component corresponding to iron ions in a paramagnetic state with an intermediate degree of valency between +2 and +3. It is shown that interpretation of the spectroscopic results using the Hamiltonian of mixed magnetic and quadrupole interactions makes it possible to obtain a vector diagram of the spatial orientations of the effective magnetic fields at the Fe57 nuclei and, as a consequence, to reconstruct the formation mechanism of the resulting vector of the magnetic moment of the yttrium iron garnet epitaxial film. Our studies reveal a slight noncollinearity of ≈4° in the orientations of the magnetic moments in the a- and d-sites of iron. The obtained results complement the picture of the magnetic and electronic hyperfine interactions in the epitaxial ferrite-garnet films and should be considered in the practical applications of the magnetic properties of such materials. © 2016, Pleiades Publishing, Ltd.