PROPERTIES OF NON - CRYSTALLINE EuIG AND DyIG OBTAINED FROM MÖSSBAUER AND MAGNETIZATION MEASUREMENTS

Abstract
Non-crystalline (nc) EuIG and DyIG have been prepared by dc-sputtering. Mössbauer data on ⁵⁷Fe, ¹⁵¹Eu and ¹⁶¹Dy reveal sharp magnetic transitions at T_m= 62 K and 70 K for nc EuIG and DyIG, respectively. The ⁵⁷Fe hyperfine (hf) spectra consist of three superpositioned patterns for Fe³⁺ in tetrahedral and octahedral and for Fe²⁺ in tetrahedral oxygen coordination. The saturation hf fields are reduced compared to the values of the corresponding crystalline materials. The induced hf field at ¹⁵¹Eu is only 1/8 of that for crystalline EuIG. The microchemical composition and structure of the nc materials can be satisfactorily explained by a small oxygen deficiency due to preferential oxygen sputtering. Macroscopic magnetization suggests ferrimagnetic order possibly of sperimagnetic type. Although a part of the deviations of the magnetic hf parameters from the values for the corresponding crystalline substances can be explained by a distribution in the molecular field, the strong reduction of T_m must be attributed to a decrease of the average molecular field due to the distorted superexchange bonds.