Dual Magnetic Resonances From Site‐Selective Doping of Hexaferrite Yielding Ultrabroadband Microwave Absorption

ABSTRACT The proliferation of 5G/6G networks and high–frequency electronics has intensifies the demand for ultrabroadband microwave absorbers, while achieving such performance in a single–phase magnetic material remains challenging due to intrinsic resonance–bandwidth limits. Herein, we report a crystallographic–site–selective rare‐earth ions co‐doping strategy to engineer magnetocrystalline anisotropy in M–type BaFe 12 O 19 (BaM) hexaferrites. By precisely substituting Sc 3+ and Yb 3+ into the anisotropy–critical 4f 2 , 2a, and 12k sublattices—confirmed via neutron powder diffraction, X–ray absorption fine structure spectroscopy, and density functional theory—the uniaxial anisotropy field is orthogonally suppressed, activating dual ferromagnetic resonance (FMR) modes. This dual resonance behavior broadens magnetic loss dispersion, redshifts natural resonance frequency, and simultaneously improves impedance matching. The optimized Ba 1.08 Fe 10.8 Yb 0.2 Sc 1.0 O 19 composition achieves an ultra‐wide effective absorption bandwidth (EAB) of 9.02 GHz (2.01 mm thickness). This study establishes an intrinsic, rare–earth–enabled design paradigm for scalable, high–performance microwave absorbers, with direct implications for electromagnetic interference suppression, stealth coatings, and next–generation wireless communication technologies.