Effect of Manganese Addition on the Structure, Magnetic Properties and Microwave Absorption of La0.8Ba0.2MnxFe½(1-x)Ti½(1-x)O3

We have carried out modification of La0.8Ba0.2MnxFe½(1 x)Ti½(1-x)O3 (x = 0.1 – 0.8) magnetic materials by wet milling method. Raw materials of La2O3, BaCO3, Fe2O3, TiO2 and MnCO3 were mixed according to stoichiometry calculation for each composition. The mixture was milled for 5 hours and then sintered at 1000 °C for 5 hours. The refinement results by Xray diffraction pattern shows that the increasing Mn composition enhances the mass fraction of La0.8Ba0.2MnxFe½(1-x)Ti½(1-x)O3 phase which has the same structure as LaMnO3. For x = 0.8 a single phase of LaMnO3 was formed. The single phase has a crystal monoclinic crystal structure with space group of I 1 2 / a 1, with lattice parameters given by a = 5.519(5) Å, b = 5.5537(5) Å and c = 7.8176(9) Å, α = γ = 90o and β = 90.345(6)o, V = 239.64(3) Å3, ρ = 6.463 gr.cm-3, wRp = 5.96, and χ2 (chi-squared) = 1.17. The hysteresis curve shows that the sample with composition x = 0.8 produces ferromagnetic behaviour at room temperature. The ferromagnetic properties arise due to the mixed valence of Mn3+ and Mn4+ ions through a double exchange mechanism. The results of the microwave absorption indicated that there was a broadening of absorption peak frequency at 9.9 GHz. The reflection loss (RL) increases with the increasing of LaMnO3 phase. For x = 0.8 we have the best of RL where the microwave absorption was calculated reaching 95% at the highest peak frequency with a thickness of 1.5 mm. Thus we have been successful in creating a single phase of La0.8Ba0.2MnxFe½(1-x)Ti½(1- x)O3 with application as a microwave absorber.