Magnetic and electric hyperfine interactions of Fe57m nuclei in compounds Y3–x Cax Fe5–x Snx O12(0.0⩽x⩽2.0)

Abstract

The effective magnetic fields at the Fe⁵⁷ nuclei in the octahedral and tetrahedral sub-lattices of the tin-substituted YIG, Y_3–xCa_xFe_5–xSn_xO₁₂(0.0⩽x⩽2.0) were investigated by the Mössbauer method. The dependence of H_eff on x obtained from the experimental results is compared with the correspondent dependence of the magnetic moments of the Fe³⁺ ions derived from the Gilleo theoretical model. The reasons for the difference in the concentration dependence of H_eff and the magnetic moment for the a-sub-lattice are discussed.

The contribution to the H_eff from the dipolar interaction of neighbouring magnetic ions was negligible in the iron garnets. The main reason for the difference in the values of H_eff in the a-and d-sub-lattices of the iron garnets is connected with the fact that the chemical bonding of Fe³⁺ ions in tetrahedral sub-lattice is partly covalent. The quadrupole effects in YIG could not be observed on the polycrystalline samples below the Curie temperature. The quadrupole splitting and the isomer shifts for the both sites of Fe³⁺ at T>T_c were observed. From the line intensity the distribution of Sn⁴⁺ and Fe³⁺ ions in the sub-lattices was obtained.