Enhanced microwave absorption in joule‐heating‐synthesized (Fe _1/3 Mn _1/3 Cr _1/3 ) ₂ AlB ₂ via dielectric–magnetic coupling

Abstract The modulation of electromagnetic parameters is crucial for enhancing the electromagnetic wave (EMW) absorption performance of materials. Here, a ternary MAB‐phase solid solution, namely (Fe 1/3 Mn 1/3 Cr 1/3 ) 2 AlB 2 (T‐FMCAB), was synthesized for the first time via rapid joule heating, overcoming the limitations associated with the synthesis of conventional MAB phases. The EMW dissipation capacity of Fe 2 AlB 2 was enhanced through the incorporation of both Cr and Mn at the Fe sites: Cr introduces strong magnetic moments, boosting the magnetic loss of the system, while Mn enhances its dielectric loss by promoting interfacial/dipole polarization through charge transitions between Mn 2+ and Mn 3+ . Defect engineering achieved through Cr/Mn co‐doping and the joule‐heating treatment further enhances dielectric and magnetic losses: the lattice distortions arising from the size mismatch among the constituent elements suppress magnetic moment switching, thereby increasing magnetic hysteresis loss, and promote the formation of defect dipoles, which dissipate energy through enhanced dipole relaxation, leading to greater dielectric loss. The prepared T‐FMCAB exhibits exceptional performance: a minimum reflection loss of −58.38 dB at an thickness of 1.47 mm and a maximum effective absorption bandwidth of 4.0 GHz. Additionally, a reduction in radar cross‐section of more than 30 dB m 2 is also observed. This work establishes a novel paradigm for developing next‐generation ultrathin, broadband, high‐performance EMW absorbers.