Improved room-temperature magnetoelectric effect and crystal structure in polycrystalline BaSrCo2Fe11AlO22

The crystal structure and the magnetoelectric (ME) effect were investigated in highly c-axis oriented polycrystalline samples of Y-type hexaferrite, BaSrCo2Fe11AlO22, fabricated using a rotating magnetic field. A detailed crystal structure was determined using a combination of scanning transmission electron microscopy and single crystal x-ray diffraction. It was revealed that Co and Al ions, which play important roles in the performance of the ME effect, reside mainly on the Fe site in the S block of the Y-type hexaferrite. In the oriented samples, electric polarization induced by applying a magnetic field reached 140 μC/m2 at 200 K and 51 μC/m2 at 300 K; consequently, the ME coefficient αH was estimated to be 7200 ps/m at 300 K. The ME performance of the oriented samples is superior to that of nonoriented polycrystalline samples and comparable with that of single crystals. Furthermore, the oriented samples allow the control of magnetization by an electric field up to 325 K. These results facilitate further investigations on room-temperature multiferroics and their practical applications.