Spectroscopic Investigation of Nano-Sized Strontium Ferrite Particles at Different Annealing Temperatures

Abstract

Strontium ferrite enjoys a high degree of chemical stability and is completely nontoxic, which makes it ideal for a wide range of applications. Magnetoplumbite-type (M-type) hexagonal strontium ferrite particles were synthesized via the sol-gel technique employing ethylene glycol as the gel precursor. The phase morphology, particle diameter, and magnetic properties of the prepared samples were studied using X-ray diffractometry (XRD), scanning electron microscope (SEM), and a vibrating sample magnetometer (VSM), respectively. The effect of temperature on the crystal structure, morphology, and magnetic studies were carried out. Also, the thermal decomposition of as- synthesized powdered samples has been studied by thermogravimetric (TG) and differential thermal analysis (DTA) methods. The optical properties were analyzed using fl uorescence spectra. The XRD results showed that the samples synthesized at 600 °C, 800 °C, and 1000 °C were of single phase and smaller crystallite size. The intensity of the emission spectra of strontium ferrite was also examined. The yield percentage along with structure determination and VSM studies of the prepared samples are discussed in detail. Introduction. The enhanced interest of researchers in nanoobjects is due to the discovery of the unusual physical and chemical properties of these objects, which is related to the manifestation of the so-called quantum size effects. A key reason for the change in the physical and chemical properties of small particles as their size decreases is the increased fraction of the surface atoms, which occur under conditions (coordination number, symmetry of the local environment, etc. differing from those of the bulk atoms. From the energy standpoint, a decrease in the particle size results in an increase in the fraction of the surface energy in its chemical potential. Currently, the unique physical properties of nanoparticles are under intensive research. A special place belongs to the magnetic properties in which the difference between a massive (bulk) material and a nanomaterial is especially pronounced. In particular, it was shown that the magnetization and magnetic anisotropy of nanoparticles can be much greater than those of a bulk specimen, while differences in the Curie (TC) or Neel (TN) temperatures, i.e., the temperatures of spontaneous parallel or antiparallel orientation of spins, between nanoparticles and the corresponding microscopic phases reach hundreds of degrees. In addition, magnetic nanomaterials were found to possess a number of unusual properties, such as giant magneto-resistance, abnormally high magnetocaloric effect, and so on. The magnetic properties of nanoparticles are determined by many factors, the key of these including the chemical composition, the type and degree of defectiveness of the crystal lattice, the particle size and shape, the morphology, and the interaction of the particle with the surrounding matrix and neighboring particles. By changing the nanoparticle size, shape, composition, and structure, one can control to a certain extent the magnetic characteristics of the material based on them. However, these factors cannot always be controlled during the synthesis of nanoparticles nearly equal in size and chemical composition; therefore, the properties of nanomaterials of the same type can be markedly different. Magnetic nanomaterials are used in information recording and storage systems, in new permanent magnets, in magnetic cooling systems, as magnetic sensors, etc. All this accounts for the interest of various specialists in these systems. A nanoparticle is a quasi-zero-dimensional (0D) nano-object in which all characteristic linear dimensions are of the same