A series of erbium-chromium substitution strontium hexaferrite particles with the nominal composition of
SrErxCrxFe12-2xO19 was synthesized using the sol-gel auto-combustion method. The crystalline structure,
magnetic and microwave absorption properties of the materials were investigated in detail. The TGA/DSC and
XRD evaluations by the FULLPROF confirmed the successful substitution of Er and Al cations in the strontium
hexaferrite lattice. Moreover, the VSM measurements confirmed that HC, and Mr continuousely decreased by
increasing the erbium and chromium substitutions, while MS increases up to x = 0.2, followed by a reduction
with the increased amount of the substitution. We also investigate the cause of the changes in the magnetic and
microwave absorption properties through simultaneous substitution. The maximum reflection loss of 34.71 dB
was observed in the SrEr0.5Cr0.5Fe11O19 sample with a bandwidth that covered the entire measured microwave
frequency range of 12–18 GHz (Ku band). This finding suggested that x = 0.5 had effective absorbing characteristics,
which is of great interests for the military radar in the Ku band.