Effects of Ba doping on the structural, magnetic and microwave absorption properties for LaMnO₃ perovskites

Manganese-based rare-earth perovskite oxides are gaining attention as microwave absorbers due to their exceptional dielectric and magnetic properties. In this study, a series of La_1−xBa_xMnO₃ (x = 0, 0.1, 0.2, and 0.3) nanoparticles were successfully prepared via the sol–gel method. The introduction of Ba²⁺ ions induces lattice distortion and reduces both crystalline and particle sizes with increasing Ba doping concentration. This process also alters the valence state of Mn ions and oxygen vacancies. Magnetic measurements display that although the magnetization curves of all samples do not reach saturation, a weak ferromagnetic ordering is observed after Ba doping, with La_0.8Ba_0.2MnO₃ exhibiting the most favorable magnetic characteristics due to enhanced double exchange interaction between Mn⁴⁺ and Mn³⁺ ions. The study highlights the controllable microwave absorption properties by adjusting Ba concentration in the LaMnO₃ system. La_0.8Ba_0.2MnO₃ demonstrates a minimum reflection loss of − 35.6 dB at 15.4 GHz with a thin matching thickness of 1.2 mm and an effective absorption bandwidth of 4.08 GHz from 13.84 to 17.92 GHz. La_0.7Ba_0.3MnO₃ achieves a remarkable minimum reflection loss of − 59.3 dB at 11.8 GHz when the matching thickness is 1.9 mm, and the corresponding effective absorption bandwidth is 3.92 GHz (9.68–13.6 GHz). These exceptional microwave absorption properties are attributed to enhanced polarization relaxation loss, conductive loss, and co-existing magnetic loss. The study suggests that the La_1−xBa_xMnO₃ synthesized via the cost-effective sol–gel method holds promise as a high-performance microwave absorber with strong absorption and lightweight characteristics.