Modulation of microwave properties of La–Sr hexagonal ferrite with doping of Co–Zr and change in thickness

Cobalt–zirconium (Co²⁺–Zr⁴⁺) doped M-type lanthanum strontium hexaferrite with general formula, Sr_0.85La_0.15(CoZr)_xFe_12−2xO₁₉ where x = 0, 0.25, 0.50, 0.75, 1.0, prepared by citrate auto-combustion method have been analyzed for the first time. These ferrites were characterized by X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscopy, vibrating sample magnetometer and vector network analyzer. The complex permittivity (ɛ′ − jɛ′′) and complex permeability (µ′ − jµ′′) were measured using vector network analyzer in 12.4–18.0 GHz (Ku-band) frequency range. Magnetic hysteresis data indicates 16.6% decrease in saturation magnetization M_s with substitution x (60.6 emu/g for x = 0.0 and 50.5 emu/g for x = 1.0). There is 53.79% decrease in coercivity H_c with substitution x (5692.55 Oe for x = 0.0 and 2630.38 Oe for x = 1.0). Microwave absorption of more than 99% has been obtained for all the synthesized ferrites at some frequency in Ku-band. So, microwave absorbers can be designed for different frequencies in Ku-band by varying the substitution x as well as thickness of the absorber.