Unlocking room-temperature magnetoelectricity in Ba1.5Sr1.5-based Z-type hexaferrites via magnetic anisotropy modulation

Abstract

Current research on room-temperature magnetoelectric (ME) Z-type hexaferrites has predominantly centered on modifications based on Sr3Co2Fe24O41, which severely restricts the compositional freedom for regulating the Ba/Sr ratio. In particular, compositions with high Ba content, exemplified by the balanced Ba1.5Sr1.5Co2Fe24O41 (Ba1.5Sr1.5-based), are traditionally regarded as incapable of hosting room-temperature ME coupling, attributed to its distinct Co2+ site preference compared to Sr-rich counterparts. In this work, we realized magnetoelectric coupling above room temperature in the Ba1.5Sr1.5-based system through Al and Cu co-substitution, altering this conventional wisdom. This doping strategy effectively modulates the magnetic anisotropy to stabilize the magnetoelectric phase up to approximately 360 K while significantly enhancing the electric polarization. Furthermore, we demonstrate that the magnetoelectric states exhibit enhanced stability against external fields. Room-temperature magnetization modulation driven by an electric field is also observed. Our findings unlock the potential of the Ba-rich Z-type system and provide a broader compositional space for designing high-performance room-temperature multiferroics.