Mossbauer study of substituted YIG, Y-Gd-Fe-In-O system

The substituted yttrium iron garnet systems Y3-xFe5-xO12 (x = 0.0, 0.18, 0.33, 0.6), Y3-xInxFe5O12 (x = 0.0, 0.18, 0.33, 0.6) and Y3-xGdxIn0.2Fe4.8O12 (x = 0.0, 0.18, 0.33, 0.6) have been investigated by means of Mossbauer spectroscopy, X-ray diffraction and superconducting quantum interference device. The X-ray diffraction patterns at room temperature confirm the samples to have a single phase of the garnet structure over the whole composition range. The lattice constants of the Y3-xInxFe5O12 and the Y3-xGdxIn0.2Fe4.8O12 systems linearly increase but that of the Y3-xFe5+xO12 system decrease with increasing x due to the size of substituted ions. The Neel temperature increases with increasing x as 510 K (x = 0.2), 520 K (x = 0.4) and 530 K (x = 0.6), which indicates the superexchange interaction is strengthened with increasing x. From the hysteresis loop measured by superconducting quantum interference device over the whole composition range, the specific magnetization a, and the number of magnetic moments eta (mu (B)) per unit cell have been obtained. The increment of Gd-ion content causes sigma (s) and eta (mu (B)) to decrease while the increment of In-ion content does not. (C) 2001 Published by Elsevier Science Ltd.