Room-temperature magnetoelectric effects in Pb-doped polycrystalline Y-type hexaferrite Ba1-xPbxSrCo2Fe11.2Al0.8O22

The realization of robust magnetoelectric (ME) coupling at room temperature in polycrystalline materials remains a pivotal challenge for practical applications. In this work, we propose and validate a novel A-site engineering strategy in Y-type hexaferrites, using Pb 2+ doping to simultaneously address the interrelated issues of low operational temperature and high leakage currents. We synthesize a series of polycrystalline ceramics with the composition Ba 1- x Pb x SrCo 2 Fe 11.2 Al 0.8 O 22 ( x = 0, 0.05, 0.1, 0.15) via a conventional solid-state reaction route. Pb 2+ doping effectively stabilizes the non-collinear alternating longitudinal conical (ALC) magnetic phase, raising its transition temperature to the proper-screw phase from 300 K to 330 K. Concurrently, PbO acts as a sintering aid, significantly enhancing the ceramic density and grain size, which leads to an intrinsic increase in electrical resistivity. For the optimal composition ( x = 0.1), we achieve an electric polarization of 16 μC/m 2 and a direct ME coefficient ( α H ) of -518 ps/m at 300 K, with P and α H increasing to 29.2 μC/m 2 and -1887 ps/m at 200 K. Moreover, the material exhibits repeatable electric polarization switching driven by low magnetic fields and clear electric-field modulation of magnetization at room temperature. Crucially, these pronounced ME effects are obtained without the need for stringent post-synthesis oxygen annealing treatments. Our results demonstrate that A-site doping with Pb 2+ provides an effective route to engineer both the magnetic phase stability and the electrical microstructure in Y-type hexaferrites, offering a promising pathway toward viable room-temperature ME devices.