Characterization of Sr-substituted W-type hexagonal ferrites synthesized by sol–gel autocombustion method

• Published in: Journal of magnetism and magnetic materials 2013-04, Vol.332, p.137-145
• Main Authors: Ahmad, Mukhtar, Grössinger, R., Kriegisch, M., Kubel, F., Rana, M.U.
• Format: Article
• Language: English
• Subjects: Analog computers; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Ferrites; Infrared; Magnetic properties; Magnetic properties and materials; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Materials selection; Mathematical analysis; Microstructure; Microwave absorption; Microwave and radio-frequency interactions (excluding resonances); Microwaves; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other interactions of matter with particles and radiation; Physics; Scanning electron microscopy; Sol-gel processes; Sol–gel; Sr-substitution; Strontium; W-type hexaferrites
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2012.12.039

The magnetic and microwave characterization of single phase hexaferrites of entirely new composition Ba1-xSrxCo2AlFe15O27 (x=0.2–1.0) for application in a microwave absorber, have been reported. The samples synthesized by sol–gel method were investigated by differential thermal analyzer, Fourier transform infrared spectroscope, X-ray diffractometer, field emission gun scanning electron microscope, vibrating sample magnetometer and vector network analyzer. Platelet grains exhibit well defined hexagonal shape which is a better shape for microwave absorption. M–H loops for a selected sample were measured for a temperature range of 4.2–400K. Moreover M–H loops for all Sr-substituted samples were also measured at room temperature up to a maximum applied field of 9T. Saturation magnetization values were calculated by the law of approach to saturation. The room temperature coercivity for all the samples is found to be a few hundred oersteds which is necessary for electromagnetic materials and makes these ferrites ideal for microwave devices, security, switching and sensing applications. The complex permittivity, permeability and reflection losses of a selected ferrite–epoxy composite were also investigated over a frequency range of 0.5–13GHz. ► Ba1-xSrxCO2AlFe15O27 hexaferrites synthesized by sol–gel method have been investigated. ► The obtained platelets grains of hexagonal shape are suitable for microwave absorbers. ► Room temperature Hc of sample is few oersteds which is necessary for EM materials. ► The peak frequency of the compounds can be tuned by varying thickness of absorber.