Synthesis and characterization of the structural and magnetic properties of the Sm3-xGdxFe5O12(x = 0.0–1.0) garnets using solid-state reaction and citrate methods

Abstract

The present work focused on synthesis and characterization of the new garnet-type materials with formula Sm3-xGdxFe5O12 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), using both the citrate and solid-state reaction methods. The influence of the substituting cation and the synthesis routes on the structural, morphological, and magnetic properties were evaluated by X-ray diffraction (XRD), Raman spectroscopy, vibrating sample magnetometry (VSM), scanning electron microscopy (SEM) and 57Fe Mössbauer spectroscopy. The results showed that Gd3+ substitution allows obtaining single-phase materials, with cubic structure and space-group symmetry Ia3¯d (230). The Gd3+ substitution modified the magnetic response of the Sm3Fe5O12 garnet, generating a decrease of the saturation magnetization (Ms), coercive field (Hc), remaining magnetization (Mr), besides, the sample with x = 1.0 exhibited a Tcomp of ≈60 K. The citrate method allowed obtaining smaller particle sizes, leading to an increase of the Hc and Mr, and decreasing the Ms, this compared with the samples obtained by the solid-state reaction method. The ferrimagnetic behavior of the materials was confirmed by room temperature 57Fe Mössbauer spectroscopy, which showed the existence of magnetic hyperfine fields and Fe3+ in the different crystallographic sites. This work shows that the use of the citrate method allows obtaining garnets of high purity and with outstanding magnetic and crystalline properties, making them applicable for transformers and microwave switches production. On the other hand, the garnets were synthesized at lower temperatures (300 °C) and less time (18 h) than those used in the solid-state reaction method, decreasing the production costs.