Investigation of structural, hysteresis and electromagnetic parameters for microwave absorption application in doped Ba–Sr hexagonal ferrites at X-band

Abstract

M-type Ba0.5Sr0.5CoxLaxFe12-2xO19 hexagonal ferrite has been synthesized by the conventional ceramic method. X-ray diffraction analysis confirmed formation of M-type hexagonal structure while scanning electron microscopy analysis revealed a reduction in grain size with the doping of Co2+ and La3+ ions. The electromagnetic/microwave absorption has been measured from 8.2 GHz to 12.4 GHz in the microwave frequency regime and substantiated through hysteresis parameters, quarter wavelength, impedance matching, loss mechanisms. The hysteresis parameters, derived from hysteresis loops, infer soft ferrite nature of compositions. The doping of Co2+ and La3+ decreases coercivity to 17 Oe in composition x = 0.2 and increases saturation magnetization to 74.2 emu/g in composition x = 1.0. The doping improves impedance matching and increases microwave absorption as well as absorption bandwidth in the prepared compositions. The pronounced multi-peaks of absorption have been observed in composition x = 0.2 and 0.4 in the investigated frequency region. The depicted reflection loss dips are tunable through doping and thickness of the compositions. The reflection loss increases to −43.33 dB in composition x = 0.2 at 10.75 GHz and 1.9 mm thickness. The composition x = 0.2 also shows −10 dB and −20 dB narrow absorption bandwidth of 300 MHz and 320 MHz respectively.