Polarization–magnetization mutual control at room temperature in polycrystalline Y-type hexaferrite Ba1− x Rb x SrCo2Fe11.2Al0.8O22

Polycrystalline Y-type hexaferrite ceramics Ba1−xRbxSrCo2Fe11.2Al0.8O22 (x = 0, 0.1, 0.2, 0.4) are engineered via A-site Rb+ doping to improve electrical insulation and magnetic-order stability in multiferroics. Substitution of Ba2+ with oversized monovalent Rb+ simultaneously suppresses Fe2+-mediated leakage through intrinsic charge compensation (resistivity: 3.51 × 109 Ω cm at x = 0.4) and elevates the alternating longitudinal conical to proper screw phase transition temperature to 346 K (x = 0.2). At the optimal composition (x = 0.2), robust room-temperature magnetoelectric coupling emerges with αH = −751 ps/m and reversible mutual control of polarization and magnetization confirmed by cyclic P–H and M–E measurements, all achieved without high-pressure oxygen annealing. This work establishes A-site alkali doping as a promising paradigm for high-resistivity multiferroic ceramics with extended operational temperature windows, advancing practical room-temperature spintronic and sensing devices.