Síntese e caracterização estrutural de óxidos semicondutores magnéticos diluídos do tipo SnO2 dopados com Fe, Co ou Mn produzidos pelo método sol-gel protéico

Abstract

The development of magnetic semiconductors has arisen growing attention due to their promising applications in spintronics. These materials can be produced by doping of a non-magnetic semiconductor with magnetic ions of transition metals. In this work, x-ray diffraction and infrared spectroscopy were used to study the structural characteristics of nanostructured Fe, Co or Mn-doped SnO2 oxide diluted magnetic semiconductors. The material was produced by a protein based sol-gel method called proteic sol-gel. To provide a basis for comparison, nanostructured standards of undoped SnO2 were produced with calcination temperatures of 300, 350 and 400◦ C. Samples of Sn1−x Mx O2−δ , where M is the magnetic dopant (Fe, Co or Mn) and x the dopant concentration, were prepared with the same calcination temperatures and x = 5, 10 and 20%. X-ray diffraction was used to identify the crystalline phases in the samples as well as to calculate structural parameters, particle sizes and residual microstrain. The analysis indicated that the synthesis resulted in nanosized compounds with the SnO2 structure. Samples calcined at 400◦ C presented the presence od spurious phases. Doping was confirmed by the variation of lattice parameters of compounds as a function of type and concentration of dopants. Vibrational modes of chemical bonds were identified by infrared spectroscopy. Based on this analysis, it was possible to study the energetic behavior of ionic bonds when doping elements are incorporated in Sn4+ sites in the host matrix.