Novel magnetoelectric composites of cobalt iron alloy and barium titanate

Abstract

Magnetoelectric barium titanate ceramics with embedded cobalt iron alloy particles (Co1/3Fe2/3)x–(BaTiO3)(1-x), with x=0.2, 0.4, and 0.6, were prepared by a polyolmediatedsynthesis with subsequent sintering in a reducing forming gas atmosphere. The samples were characterized by XRD and SEM/EDX measurements. The sizes of the Co1/3Fe2/3 grains increase with x. Impedance spectroscopy showed a behavior similar to pure BaTiO3, in particular the occurrence of the ferroelectric-paraelectricphase transition, and high permittivities for the sample with x=0.6, that is, near the percolation threshold. The samples exhibit soft ferromagnetic properties with largesaturation magnetizations of 2.5 lB/atom and narrow hystereses. Detailed magnetoelectricinvestigations revealed a unique DC-field dependence of aME for all threecompositions. Most remarkably, the sample with x=0.4 possesses a broad ME hysteresisand an inversion of the sign of aME at 5 kOe.