Anomalous Magnetoelectric Coupling Effect of CoFe₂O₄–BaTiO₃ Binary Mixed Fluids

Abstract

We report an anomalous magnetoelectric coupling effect of CoFe 2 O 4 −BaTiO 3 binary mixed fluids, which were prepared by distributing surfactant treated (oleic acid) magnetic CoFe 2 O 4 and ferroelectric BaTiO 3 nanoparticles into highly insulating base fluid (silicone oil). A strong coupling effect in this mixed fluid has been observed, in which both the remnant polarization/magnetization and coercive electric/magnetic field are found to be enhanced visibly in the presence of an external magnetic/electric field. Colossal converse and direct magnetoelectric coupling coefficients are estimated to be α H = 1.22 × 10 −4 Oe•cm/V and α E = 2.52 × 10 4 V/(cm•Oe), respectively. Moreover, this coefficient clearly depends on the volume fraction of the two kinds of particles and the applied external magnetic/electric field. Even more amazing, CoFe 2 O 4 also shows a strong magnetoelectric coupling effect with a coefficient as high as 4.2 × 10 −5 Oe•cm/V. Further analysis indicates that the aggregated, chain-like structure of the particles under the action of external fields is believed to be responsible for the clamping effect, which in turn induces the observable anomalous coefficient. The field generated chain-like structure shows intense relaxation behavior with a relaxation time of several minutes. These results provide valuable information for enhancing the coupling effect of mixed fluids and may be important for practical applications in magnetoelectric devices.

A comparative study on the structural, dielectric, ferroelectric and magnetic properties of CoFe2O4/PbZr0.52Ti0.48O3 multiferroic composite with different molar ratios

“…For instance, when the temperature is 400°C, the dielectric loss of all the specimens at 1000 kHz is less than 1, but this value increased suddenly with the decrease of frequency, the value is larger than 5 at 10 kHz, 50 at 1 kHz and 500 at 100 Hz. With the increase of frequency, the polarization relaxation loss increases and the leakage loss decreases [22][23][24][25].…”

“…In order to achieve strong magnetoelectric coupling effect, it is necessary to improve the magnetic/ferroelectric properties under the action of an electric/magnetic field. It has been found that by adjusting the composition of the composite material, the magnetic/ferroelectric properties can be effectively adjusted to improve the magnetoelectric coupling coefficient [22][23][24][25][26][27][28]. Till now, several composite materials have been studied, including Co 0.5 Ni 0.…”

Influence of molar ratio on dielectric, ferroelectric and magnetic properties of Co0.5Mg0.5Fe2O4/Ba0.85Sr0.15TiO3 composite ceramics

“…To directly show the density of the prepared ceramics with different molar ratios, Archimedes principle was applied. When the molar ratios are 1:1, 1:2, 1:4, 1:6 and 1:8, the corresponding densities of the samples are 5.271, 5.267, 5.325, 5.371 and 5.450 g/cm 3 , respectively. The relative density was calculated using the ratio of the measured density to the theoretical density.…”

“…Multiferroic material is a new kind of functional material which can show magnetic and ferroelectric properties simultaneously [1][2][3]. In the past several decades, multiferroic materials have attracted great attention not only due to their intriguing physical properties, but also because of their potential applications in sensor, capacitor, information storage, energy harvesting, spintronics etc.…”

“…However, this is limited in the single phase multiferroic materials, since the Curie temperature of the magnetic and (or) ferroelectric order is always far below room temperature. Due to BiFO 3 having high both the Curie temperature (∼1100 K) and Neel temperature (∼640 K) [8][9][10], a very few room temperature single L. Bai et al / Processing and Application of Ceramics 13 [3] (2019) 257-268 phase multiferroic materials are known so far. The ME effect is still very weak because of the G-type antiferromagnetic ordering in bismuth ferrite and the serious leakage current induced by impurities and defects such as oxygen vacancies [11][12][13].…”