D. A. Filippov

Giant magnetoelectric effect in composite materials in the region of electromechanical resonance

The magnetoelectric effect in multilayer ferrite-piezoelectric composites has been theoretically and experimentally studied. Using the method of effective parameters, an expression for the magnetoelectric coefficient is determined and its frequency dependence is analyzed. It is shown that, in the region of electromechanical resonance, the magnitude of the effect exceeds a low-frequency value by more than an order of magnitude. The results of calculations obtained for a nickel ferrite spinel-PZT composite are in good agreement with the experimental data.

Resonant amplification of the magnetoelectric effect in ferrite-piezoelectric composites

The magnetoelectric effect in ferrite-piezoelectric composites is considered. A theory of the magnetoelectric effect in the electromechanical-resonance region for disk-shaped samples is presented. The magnetooptical coefficient is calculated for longitudinal and transverse orientations of electric and magnetic fields. It is shown that the effect increases by a few orders of magnitude at the electromechanical-resonance frequency. The frequency dependence of the effect is experimentally studied for a ferrite-nickel spinel-PZT composite. A resonant increase in the effect is observed (in agreement with the theory); the highest value of the magnetoelectric coefficient was 15 V/(cm Oe).

Magnetoelectric effect in a magnetostrictive-piezoelectric bilayer structure

The results of theoretical and experimental investigations of the magnetoelectric effect in a magnetostrictive-piezoelectric bilayer structure have been presented. The expression for the magnetoelectric voltage coefficient in the region of electromechanical resonance has been derived based on the joint solution of the equations of motion for the magnetostrictive and piezoelectric media and the constitutive relations. The dependence of the magnitude of the effect on the thickness of the ferrite and piezoelectric layers has been analyzed. The experimental results for nickel-lead zirconate-titanate bilayer structures have been reported. The theoretical results agree perfectly with the experimental data.

Inverse magnetoelectric effect in disk-shaped samples of ferrite piezoelectric composites

A theory of the inverse magnetoelectric effect in the vicinity of electromechanical resonance in disk-shaped samples is presented. An expression for the coefficient of the inverse magnetoelectric transformation has been obtained using the effective parameter method. It has been shown that a sharp increase in the magnitude of the effect occurs at a frequency of electromechanical resonance, and the resonance frequencies for the direct and inverse magnetoelectric effects are different. The dependences of the resonance frequencies on the ferrite percentage in ferrite-nickel spinel samples and lead zirconate titanate samples have been studied experimentally.

Inverse magnetoelectric effect in ferrite-piezoelectric structures

A theory of the inverse magnetoelectric (ME) effect in bulk ferrite-piezoelectric composite materials is presented. Using the material equations and equations of motion, expressions for the frequency dependence of the inverse ME conversion coefficient and the voltage ratio in an ME transformer are obtained. These dependences exhibit a resonant character, with the ME response magnitude peaking at the resonance frequency. The ME transformer coefficient not only depends on the ME voltage coefficient and the number of turns in the induction coil, but is also influenced by the mutual orientation of the electric and magnetic fields and the sample geometry.

Voltage transformer based on inverse magnetoelectric effect

A voltage transformer, the operation of which is based on the inverse magnetoelectric effect, has been studied. The device comprises a nickel-PZT-nickel trilayer capacitor structure on which an induction coil is wound. It is established that the frequency dependence of the output signal has a resonance character and the transmission characteristic is linear in a broad range of input voltages.

Nonlinear magnetoelectric effect in composite multiferroics

The theoretical and experimental studies of the nonlinear magnetoelectric effect in composite multiferroics in the low-frequency spectral region and in the electromechanical resonance region have been performed. It has been shown that such structures demonstrate a nonlinear magnetoelectric effect, which is quadratic in ac magnetic field strength at weak magnetic fields. In the region of the electromechanical resonance, the resonance excitation of an electric field occurs by means of ac magnetic field at a frequency lower than the resonance frequency by a factor of two. In the low-frequency spectral region, there is a difference of amplitude values of two neighboring voltage maxima due to the superposition of signals from the linear and nonlinear effects, and the difference is proportional to the dc magnetic field strength in weak fields. The results of the experimental study of the two-layer permendur-lead zirconate titanate structure are presented.

Magnetoelectric effect in thin-film magnetostriction-piezoelectric structures grown on a substrate

The theory of the magnetoelectric effect in a thin magnetoelectric film-passive substrate structure is presented. Based on the simultaneous solution of the constitutive equations and the equations of motion for the film and substrate, the dispersion law has been derived for elastic waves propagating in the sample plane. It has been shown that the elastic vibrations in the substrate propagate in a near-surface layer if the velocity of propagation of elastic vibrations in the substrate is higher than that in the magnetoelectric film. In this case, the substrate thickness almost does not influence the magnitude of the effect.

The magnetoelectric effect in nickel–GaAs–nickel structures

We have experimentally studied the magnetoelectric (ME) effect in structures obtained by the electrolytic deposition of nickel onto gallium arsenide substrates. It is established that the use of a pre-deposited Ni–Au–Ge–Ni buffer sublayer significantly improves the adhesion of electroplated nickel to substrate. The resulting Ni–GaAs–Ni structures are featuring both linear and nonlinear ME effects with respect to the alternating magnetic field. Both these effects exhibit a resonance character, the resonance frequency of the nonlinear ME effect being two times lower than that for the linear effect.

The magnetoelectric effect in the ring shape magnetostrictive-piezoelectric structures

We have theoretically and experimentally studied the direct magnetoelectric (ME) effect in ring structures made of volume ferrite–piezoelectric composites based on lead zirconate titanate and nickel ferrite. Analytical expressions for the ME voltage coefficient are obtained by jointly solving elastodynamic and electrostatic equations. Results of theoretical calculations and experimental measurements for various geometric parameters of the ring structures are presented.