Fine-grained magnetoelectric Sr0.5Ba0.5Nb2O6–CoFe2O4 composites synthesized by a straightforward one-pot method

Magnetoelectric (Sr0.5Ba0.5Nb2O6)1x(CoFe2O4)x (x = 0.2–0.6) composites were prepared by a one-pot softchemistrysynthesis using PEG400. Calcining at 700 ◦C resulted in nanocrystalline composite powders (dcryst. =24–30 nm) which were sintered between 1050 and 1200 ◦C to ceramic bodies with relative densities up to 98%.SEM investigations confirm the formation of composite ceramics with a 0–3 connectivity and variable grain sizesfrom 0.2 to 3.6 μm for sintering up to 1150 ◦C, while sintering at 1200 ◦C leads both to a change in themicrostructure and a considerable grain growth. Magnetic measurements at 300 K reveal ferrimagnetic behaviourwith saturation magnetization values smaller than bulk CoFe2O4 and coercivities between 790 and 160 Oe.Temperature-dependent impedance spectroscopy showed that the relative permittivities decrease both withrising frequency and CoFe2O4 fraction. The frequency dependence of the impedance can be well described usinga single RC circuit. Magnetoelectric measurements show the presence of pronounced field hystereses. Themaximum magnetoelectric coefficient (αME) depends both on the CoFe2O4 fraction (x) and sintering temperature.The composite with x = 0.3 exhibits the largest αME value of 37 μV Oe1 cm1 (@ 900 Hz). With rising frequencyof the AC driving field αME increases up to 300–400 Hz and is nearly constant until 1 kHz.

Magnetoelectric, magnetodielectric and magneto-impedance couplings in Bi1−xNdxFe0.99Co0.01O3 compounds

In this work Bi1−xNdxFe0.99Co0.01O3 ceramics compositions were synthesized for x = 0.05, 0.20 and, y = 0.01. Structural refinement results show that most of the samples crystallized in a rhombohedral symmetry with R3c. Measurements magnetoelectric coefficient, show that the magnetoelectric coefficients are of second order. The electrical impedance characterization of in function external magnetic fields, has a relative variation of the real dielectric response, the loss tangent and the electrical impedance. The systems, as the DC magnetic field strength increased a gain in both the values of the dielectric constant variation, as well as the variation of the electrical impedance. In other words, the greater the intensity of the magnetic field, the greater your response. There were also significant variations with of the magnetic field AC.

All organic multiferroic magnetoelectric complexes with strong interfacial spin-dipole interaction

The organic magnetoelectric complexes are beneficial for the development on flexible magnetoelectric devices in the future. In this work, we fabricated all organic multiferroic ferromagnetic/ferroelectric complexes to study magnetoelectric coupling at room temperature. Under the stimulus of external magnetic field, the localization of charge inside organic ferromagnets will be enhanced to affect spin–dipole interaction at organic multiferroic interfaces, where overall ferroelectric polarization is tuned to present an organic magnetoelectric coupling. Moreover, the magnetoelectric coupling of the organic ferromagnetic/ferroelectric complex is tightly dependent on incident light intensity. Decreasing light intensity, the dominated interfacial interaction will switch from spin–dipole to dipole–dipole interaction, which leads to the magnetoelectric coefficient changing from positive to negative in organic multiferroic magnetoelectric complexes.

Doping Effect on Piezoelectric, Magnetic and Magnetoelectric Properties of Perovskite—Ferromagnetic Magnetoelectric Composites

This chapter explains the effect of compositional modification on the magnetoelectric coefficient in sintered piezoelectric – magnetostrictive composites. It was found that 15 at% doping of Pb(Zn1/3Nb2/3)O3 [PZN] in Pb(Zr0.52Ti0.48)O3 [PZT] enhances the piezoelectric and magnetoelectric properties of a PZT – 20 at% Ni0.8Zn0.2Fe2O4 [NZF] composite. The effect of doping on the ferromagnetic phase was also investigated. With increases in Zn concentration, it was found that the coercive field and Curie temperature of Ni(1-x)ZnxFe2O4 [NZF] decreases, while its saturation magnetization has a maxima at 30 mole% Zn. X-ray diffraction revealed that the lattice constant of NZF increases from 8.32 Å for 0 at% Zn to 8.39 Å for 50 at% Zn. The magnetoelectric coefficient was found to have a maxima of 144 mV/cm.Oe at 30 at% Zn. To understand better, the effect of 40% (by mole) Zn substitution on structural, piezoelectric, ferromagnetic and magnetoelectric properties of Pb(Zr0.52Ti0.48)O3 - CoFe2O4 (PZT - CFO) sintered composite is also explained. X-ray diffraction of Co0.6Zn0.4Fe2O4 (CZF) showed the shift in almost all diffraction peaks to lower diffraction angle confirming the increase in lattice parameter in all three direction from 8.378 (for CFO) to 8.395 Å for (Co,Zn)Fe2O4 (CZF). SEM and TEM results showed defect structure (cleavage, twins, strain fields) in the CZF particle, which is a clear indication of misfit strain developed due to lattice expansion. Magnetic properties measured over temperature (5 K – 1000 K) showed increased magnetization but lower magnetic Curie temperature in PZT - CZF particle. Magnetoelectric coefficient measured as function of ferrite concentration showed an increase of more than 100% after doping the CFO phase with 40% Zn. This enhancement can be attributed to increase in the lattice strain, magnetic permeability and decrease in coercivity.

Магнитоэлектрический эффект в трехслойных асимметричных структурах в области изгибных мод колебаний

A theory of the magnetoelectric effect in three-layer asymmetric structures composed of a piezoelectric layer and two magnetostriction layers with opposite magnetostriction signs is presented. The thickness ratio of the layers is obtained, at which this effect is maximum. It is shown that the sign of the magnetoelectric coefficient changes to opposite (with respect to the initial two-layer structure) with an increase in the third-layer thickness. It is established that the magnetoelectric coefficients of the structures with different arrangements of the layers with positive and negative magnetostriction have opposite signs.

Магнитоэлектрические свойства мультиферроиков BiFeO-=SUB=-3-=/SUB=- замещенных цинком

The magnetoelectric properties of ceramic samples of multiferroics BiFe1-xZnxO3 and Bi1-xZnxFe1-xZnxO3 were studied in the magnetic field from 0 to 80 kOe at room temperature. All samples have linear dependences of the magnetoelectric coefficient αME with small hump-like maxima αME both at c 10 kHz and at 85 kHz. Magnetoelectric studies in samples of bismuth ferrite series with double substituted Zn show that double substitution of Bi3+ and Fe3+ ions by Zn2+ ions does not give the desired enhancement of magnetoelectric properties.

Магнитоэлектрический эффект в двухслойных композитах с градиентной магнитной фазой

The samples of homogeneous (x = 0; 0.1; 0.2) and multilayer ceramics with compositional gradient (х = 0.2 → 0.1 → 0 → 0.1 → 0.2) based on solid solutions of nickel – zinc ferrites (Ni1–xZnx) Fe2O4 have been prepared by thick-film technology. The graded samples had smooth inhomogeneous distribution of chemical elements (Zn, Ni) throughout the thickness after sintering by the two-stage mode. The longitudinal (αE33) and transverse (αE31) magnetoelectric effects in bilayer PZT – nickel – zinc ferrite composites were studied. Magnetoelectric coefficients were not significant in the absence of an external constant magnetic field. The maximum value of the longitudinal magnetoelectric coefficient in composites with graded magnetic phase was almost two times higher than the value of αE33 in homogeneous structures.