The nano-sized of La0.7Sr0.3Mn1−xCoxO3 (x=0, 0.2, 0.4, 0.6, 0.8)(LSMCO) powders were synthesized using a simple sol-gel method. For measuring microwave absorption properties, micro- sized carbonyl iron (CI)/LSMCO composites were prepared with the weight ratio of 75:5. The composite materials in the form of paints were applied on an aluminum substrate with a coating thickness of 0.7, 0.9 and 1.1 mm, respectively. Phase analysis of the products, morphology observation of particles, analysis of the element composition, the magnetic properties of the powders and the electromagnetic (EM) wave parameters were determined using x-ray diffraction analysis (XRD), field emission scanning electron microscopy (FE-SEM), dispersive spectroscopy (EDS), magnetometer (VSM) and vector network analysis (VNA), respectively. According to SEM observations, the average diameter of the La0.7Sr0.3Mn1−xCoxO3(x=0, 0.6) powders is about 30 and 36 nm, respectively. Room temperature magnetization results show a soft magnetic and ferromagnetic behavior of the CI, LSMCO powder. The CI/La0.7Sr0.3Mn0.4Co0.6O3 composite showed a maximum reflection loss of— 9.6 dB at 11.38 GHz with the thickness of 0.9 mm. By increasing the thickness of coating from 0.7 to 1.1 mm, the average absorption properties were increased.
