Anisotropic Spin-Driven Ferroelectricity And Magnetoelectric Effect In A Y-Type Hexaferrite

We report a systematic study on the magnetic, dielectric, and magnetoelectric (ME) properties of the Y-type hexaferrite (Ba0.4Sr1.6)Zn-2(Fe11.3Al0.7)O-22 single crystal. The phase diagrams were established by the observed magnetic anomalies under magnetic field and temperature scans for the in-plane and out-of-plane cases. Intrinsic large anisotropy in the magnetodielectric and converse ME effects was revealed. The spin-driven electric polarizations induced in the ab-plane and out-of-plane were found to be closely related to the transverse conical and alternating longitudinal conical spin structures, respectively. The amplitudes of varied magnetization Delta M are about similar to 0.128 mu (B)/f.u and similar to 0.0178 mu (B)/f.u. in the E oscillating between +/- 1MV/m at 100K, corresponding to the converse ME effect coefficient of similar to 3500 ps/m and similar to 480 ps/m for the in-plane and out-of-plane cases, respectively. All these results demonstrate the essential and unique spin-order-induced anisotropic ferroelectricity and ME properties in these Y-type hexaferrites.