Composition control of magnetoelectric relaxor behavior in multiferroic BaZr0.4Ti0.6O3/CoFe2O4 composites

Abstract The (BaZr 0.4 Ti 0.6 O 3 ) 1 − x /(CoFe 2 O 4 ) x (abbreviated as BZT 1 − x /CFO x ; x = 0.10, 0.15, 0.20 and 0.25) polycrystalline composites are synthesized by a high-temperature solid state reaction technique. The effect of CFO composition on magnetoelectric-relaxor characteristics of the composites is thoroughly investigated. Detailed structural analysis of the composites by Rietveld refinement technique and first principles based density functional calculations reveal a macroscopic cubic structure with coexistence of P m 3 ¯ m (for BZT), F d 3 ¯ m (for CFO) space groups and a microscopic lower symmetry tetragonal structure with P 4mm space group (indicating the presence of polar-nano-regions). To probe the relaxor behavior, the dielectric measurements were carried out in the wide frequency (1 kHz–1 MHz) and temperature (90–300 K) domain. It is observed that all the composite samples exhibit low temperature ferroelectric behavior. For some composite samples (0.10 ≤ x ≤ 0.20), the ferroelectricity is of relaxor-type. The relaxor behavior of the materials was further explained by Vogel–Fulcher type freezing of polar-nano-regions. The composite sample with x = 0.25, exhibits diffuse type ferroelectric phase transition with high value of diffusivity parameter (γ = 1.98). Though BZT is paraelectric at room temperature, nevertheless the appearance of saturating P–E loops, gradual enhancement of remnant polarization with CFO ratio and co-occurrence of saturating M−H loops confirm the room temperature magnetoelectricity in composites. The impedance spectroscopic method is also employed to explain the influence of the conduction mechanism on ferroelectricity. The BZT/CFO composites with low temperature relaxor/diffuse phase ferroelectricity and room temperature magnetoelectricity can be exploited for both capacitor and memory device applications.