Improved room-temperature magnetoelectric coupling properties for multiferroic Z-type hexaferrites

Here we present the results of a systematic investigation of the effect of Ba substitution on the spiral magnetic structure and magnetoelectric effect in polycrystalline BaxSr3_xCo2Fe24O41 (x = 0.0, 0.1, 0.3, 0.5, and 0.7). The magnetoelectric coupling coefficient was improved from 455 ps/m (x = 0.0) to 624 ps/m (x = 0.3). Furthermore, the magnetic field range at which the magnetoelectric signal appears extended from 0--0.4 T (x = 0.0) to 0-0.9 T (x = 0.5), demonstrating that the transverse conical spin structure was significantly strengthened by Ba substitution. These improvements are attributed to the decrease of Fe-O-Fe bond angle near the L and S blocks boundary, the reduction of cone angle in the transverse conical spin structure, and the change in the distribution of magnetic Co ions caused by the substitution of large Ba ions for small Sr ions. In general, we achieved the improved magnetoelectric coupling strength in polycrystalline Z-type hexaferrite for the first time.

Automated summary

In this study, the effect of Ba substitution on the spiral magnetic structure and magnetoelectric effect in polycrystalline Z-type hexaferrites was systematically investigated. The results showed that Ba substitution significantly improved the magnetoelectric coupling coefficient and extended the magnetic field range for the appearance of magnetoelectric signals. These improvements were attributed to the decrease of Fe-O-Fe bond angle, reduction of cone angle in the transverse conical spin structure, and change in the distribution of magnetic Co ions caused by Ba substitution.