The chirality-dependent magnetoelectric properties of Neel-type domain walls in iron garnet films is observed. The electrically driven magnetic domain wall motion changes the direction to the opposite with the reversal of electric polarity of the pro
be and with the chirality switching of the domain wall from clockwise to counterclockwise. This proves that the origin of the electric field induced micromagnetic structure transformation is inhomogeneous magnetoelectric interaction.
Various phenomena related to inhomogeneous magnetoelectric interaction are considered. The interrelation between spatial modulation of order parameter and electric polarization, known as flexoelectric effect in liquid crystals, in the case of magneti
c media appears in a form of electric polarization induced by spin modulation and vice versa. This flexomagnetoelectric interaction is also related to the influence of ferroelectric domain structure on antiferromagnetic vector distribution, and to the magnetoelectric properties of micromagnetic structures. The influence of inhomogeneous magnetoelectric interaction on dynamic properties of multiferroics, particularly magnon spectra is also considered.
Magnetic phase transitions in multiferroic bismuth ferrite (BiFeO3) induced by magnetic field, epitaxial strain, and composition modification are considered. These transitions from a spatially modulated spin spiral state to a homogenous antiferromagn
etic one are accompanied by the release of latent magnetization and a linear magnetoelectric effect that makes BiFeO3-based materials efficient room-temperature single phase multiferroics.
There is a profound analogy between inhomogeneous magnetoelectric effect in multiferroics and flexoelectric effect in liquid crystals. This similarity gives rise to the flexomagnetoelectric polarization induced by spin modulation. The theoretical est
imations of flexomagnetoelectric polarization agree with the value of jumps of polarization in magnetoelectric dependences (~20muC/m^2) observed at spin cycloid suppression at critical magnetic field 200kOe.
The experimental studies of magnetoelectric effects in pulse magnetic field up to 250 kOe and their theoretical analysis on the basis of magnetic symmetry consideration are carried out. It is shown that the nonvanishing components of quadratic magnet
oelectric effect tensor corresponding to the electric polarization along b- and c-axes point out the triclinic distortion of the crystal symmetry. Anomalous temperature dependence of magnetically induced polarization Pa(Hb) testifies to the magnetically induced pyroelectric effect. The torque curves measurements show the deflection of the spin orientation from the b-axis at 9 degrees of arc.
The dynamic observation of domain wall motion induced by electric field in magnetoelectric iron garnet film is reported. Measurements in 800 kV/cm electric field pulses gave the domain wall velocity ~45 m/s. Similar velocity was achieved in magnetic
field pulse about 50 Oe. Reversible and irreversible micromagnetic structure transformation is demonstrated. These effects are promising for applications in spintronics and magnetic memory.
The paper shows that silicon-based 2D photonic crystal can be a promising material for acoustooptical devices. Isotropic and anisotropic Bragg diffraction of light in photonic crystal is considered. The computational method for calculation of frequen
cy dependences of Bragg angle is developed. A simple method of optimization of photonic crystal parameters to obtain Bragg diffraction at necessary light and sound frequency is suggested.
The room temperature magnetoelectric effect was observed in epitaxial iron garnet films that appeared as magnetic domain wall motion induced by electric field. The films grown on gadolinium-gallium garnet substrates with various crystallographic orie
ntations were examined. The effect was observed in (210) and (110) films and was not observed in (111) films. Dynamic observation of the domain wall motion in 400 V voltage pulses gave the value of domain wall velocity in the range 30-50 m/s. The same velocity was achieved in magnetic field pulse about 50 Oe.
The effect of magnetic domain boundaries displacement induced by electric field is observed in epitaxial ferrite garnet films (on substrates with the (210) crystallographic orientation). The effect is odd with respect to the electric field (the direc
tion of wall displacement changes with the polarity of the voltage) and even with respect to the magnetization in domains. The inhomogeneous magnetoelectric interaction as a possible mechanism of the effect is proposed.
