Concentration and temperature-dependent magnetic properties of ba1xznxfe12o19 hexaferrites
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Abstract
In the present study two sets of nanocomposites consisting of an epoxy resin and BaFe12O19 or SrFe12O19nanoparticles were successfully developed and characterized morphologically and structurally via scanning electron microscopy and X-ray diffraction spectra. The dielectric response of the nanocomposites was investigated by means of broadband dielectric spectroscopy and their magnetic properties were derived from magnetization tests. Experimental data imply that the incorporation of the ceramic nanoparticles enhances significantly the dielectric properties of the examined systems and their ability to store electrical energy. Dielectric spectra of all systems revealed the presence of three distinct relaxation mechanisms, which are attributed both to the polymer matrix and the nanoinclusions: Interfacial polarization, glass to rubber transition of the polymer matrix and the re-orientation of small polar side groups of the polymer chain. The magnetic measurements confirmed the ferromagnetic nature of the nanocomposites. The induced magnetic properties increase with the inclusion of hexaferrite nanoparticles. The nanocomposites with SrFe12O19nanoparticles exhibit higher values of coercive field, magnetization, magnetic saturation and remanence magnetization. A magnetic transition was detected in the ZFC/FC curves in the case of the BaFe12O19/epoxy nanocomposites.
Keywords: barium ferrite, strontium ferrite, ferromagnetic nanocomposites, dielectric relaxations, magnetization, zero field cooled, field cooled, magnetic transition
1. Introduction
Ferrites belong in a large and well-established class of ceramic magnetic materials with a wide range of technological applications [1]. Ferrites are classified into two major types, the soft magnets characterized by domain walls which easily can be moved by an externally applied magnetic field and the hard magnets that are chemical compounds of metal oxides with strong magnetic properties, which are ideal for permanent magnets [2]. The M-type hexaferrites MFe12O19 (M = Ba, Sr or Pb) are important ferromagnetic oxides and have traditionally be used as permanent magnets in applications for dielectric media because of their high values of magneto-crystalline anisotropy and saturation magnetization. Because of their chemical stability, high intrinsic coercivity, large crystal anisotropy, high electrical resistivity, low cost, enhance resistance to the heat and high corrosion resistance, ferrites can be employed as components in a variety of microwave and high frequency electronic devices, used in magnetic recording media,