The Direct and the Converse Magnetoelectric Effect in Multiferroic Cobalt Ferrite–Barium Titanate Ceramic Composites

Abstract

We report on a systematic study of the magnetoelectric effect in cobalt ferrite (CoFe2O4)—barium titanate (BaTiO3) ceramic composites with (0‐3) connectivity. Both the converse magnetoelectric coefficient, αC, and the direct voltage magnetoelectric coefficient, αE, were measured in dependence on composition and electric and magnetic bias fields. The strongest ME effect was observed in the composition (1−x) CoFe2O4–xBaTiO3 with x = 0.5 yielding values αC = 25 psm−1 and αE = 3.2 mV/(cm·Oe). We show that the proper conversion between these two coefficients demands knowledge about the dielectric permittivity of the sample. For low BaTiO3 content the dielectric coefficient of the composite yields a better correspondence, whereas for high BaTiO3 content the sample's average dielectric coefficient yields a better match. The influence of mutual orientation of polarization and magnetization on the ME effect is addressed. We found that for measurements performed parallel to the polarization direction (longitudinal effect), the ME coefficient is approximately twice as large and of opposite sign in comparison to the measurements perpendicular to the polarization direction (transverse effect). This difference has been rationalized in terms of the different contributions of the material coefficient tensor components to the ME effect, the demagnetizing factor, and losses. The obtained results provide a better understanding of peculiarities of the ME effect in bulk ceramic composites.

Finite element simulation of nonlinear magnetoelectric coupling and damage behaviour in multiferroic composites

“…2: a): Damage pattern of a ME particle composite (0.2CoFe2O4-0.8BaTiO3, matrix: BaTiO3) right after electric poling with E1=5Ec and magnetic loading with H1=1000 kA/m. The local damage parameter f=1 indicates full damage and thus macro crack formation, b) and c): average electric displacement and ME coupling coefficient from numerical simulation; experimental values from [7,8] Based on the material models, in particular nonlinear simulations have been done in order to predict ME coupling coefficients [6]. The residual stresses induced during the poling process will lead to substantial cracking, thus further reducing the ME coupling, see Fig.…”

First-time synthesis of a magnetoelectric core–shell compositeviaconventional solid-state reaction

“…(100) c planes for perovskites and (200) c planes for spinells are similar. Many ME composite materials have been realized for example in the systems BaTiO 3 -CoFe 2 O 4 , [15][16][17] or BiFeO 3 -CoFe 2 O 4 , 18,19 and some also with core-shell type structures such as core-shell fibers. 20,21…”

Magnetoelectric coupling in nanoscale 0–1 connectivity

“…In particular, particulate composites consisting of MS particles within a bulk PE material is known as 0-3 connectivity, [9][10][11] laminate composites comprising MS and PE layers are in a 2-2 connectivity, [12][13][14] and heterostructural composites with MS rods embedded in a PE bulk are defined as 1-3 connectivity. [15][16][17][18] These aforementioned connectivities are well-studied however novel connectivities are emerging and being explored for their ME properties.…”