Interfacial Dzyaloshinskii-Moriya interaction (DMI) is experimentally investigated in Pt/Co/Pt multilayer films under strain. A strong variation (from 0.1 to 0.8 mJ/m 2 ) of the DMI constant is demonstrated at ±0.1% in-plane uniaxial deformation of the films. The anisotropic strain induces strong DMI anisotropy. The DMI constant perpendicular to the strain direction changes sign while the constant along the strain direction does not. Estimates are made showing that DMI manipulation with an electric field can be realized in hybrid ferroelectric/ferromagnetic systems. So, the observed effect opens the way to manipulate the DMI and eventually skyrmions with a voltage via a strainmediated magneto-electric coupling.

We report an experimental study of the optical properties of a two-dimensional square lattice of triangle Co and CoFe nanoparticles with a vortex magnetization distribution. We demonstrate that the intensity of light scattered in the diffraction maxima depends on the vorticity of the particles' magnetization and can be manipulated by applying an external magnetic field. The experimental results can be understood in terms of simple phenomenological consideration.

We study influence of image forces on conductance of ferroelectric tunnel junctions. We show that the influence of image forces is twofold: i) they enhance the electro-resistance effect due to polarization hysteresis in symmetric tunnel junctions at non-zero bias and ii) they produce the electro-resistance effect due to hysteresis of dielectric permittivity of ferroelectric barrier. We study dependence of ferroelectric tunnel junction conductance on temperature and show that image forces lead to strong conductance variation with temperature.

We study electron transport properties of composite ferroelectrics -materials consisting of metallic grains embedded in a ferroelectric matrix. In particular, we calculate the conductivity in a wide range of temperatures and electric fields, showing pronounced hysteretic behavior. In weak fields, electron cotunneling is the main transport mechanism. In this case, we show that the ferroelectric matrix strongly influences the transport properties through two effects: i) the dependence of the Coulomb gap on the dielectric permittivity of the ferroelectric matrix, which in turn is controlled by temperature and external field; and ii) the dependence of the tunneling matrix elements on the electric polarization of the ferroelectric matrix, which can be tuned by temperature and applied electric field as well. In the case of strong electric fields, the Coulomb gap is suppressed and only the second mechanism is important. Our results are important for i) thermometers for precise temperature measurements and ii) ferrroelectric memristors.

We report on results of computer micromodelling of anti-vortex states in asymmetrical cross-like ferromagnetic nanostructures and their practical realization. The arrays of cobalt crosses with 1 μm branches, 100 nm widths of the branches and 40 nm thicknesses were fabricated using e-beam lithography and ion etching. Each branch of the cross was tapered at one end and bulbous at the other. The stable formation of anti-vortex magnetic states in these nanostructures during magnetization reversal was demonstrated experimentally using magnetic force microscopy.

We study magnetic state and electron transport properties of composite multiferroic system consisting of a granular ferromagnetic thin film placed above the ferroelectric substrate. Ferroelectricity and magnetism in this case are coupled by the long-range Coulomb interaction. We show that magnetic state and magneto-transport strongly depend on temperature, external electric field and electric polarization of the substrate. Ferromagnetic order exists at finite temperature range around ferroelectric Curie point. Outside the region the film is in the superparamagnetic state. We demonstrate that magnetic phase transition can be driven by an electric field and magneto-resistance effect has two maxima associated with two magnetic phase transitions appearing in the vicinity of the ferroelectric phase transition. We show that positions of these maxima can be shifted by the external electric field and that the magnitude of the magneto-resistance effect depends on the mutual orientation of external electric field and polarization of the substrate.

Composite multiferroics are materials exhibiting the interplay of ferroelectricity, magnetism, and strong electron correlations. Typical example -magnetic nano grains embedded in a ferroelectric matrix. Coupling of ferroelectric and ferromagnetic degrees of freedom in these materials is due to the influence of ferroelectric matrix on the exchange coupling constant via screening of the intragrain and intergrain Coulomb interaction. Cooling typical magnetic materials the ordered state appears at lower temperatures than the disordered state. We show that in composite multiferroics the ordered magnetic phase may appear at higher temperatures than the magnetically disordered phase. In non-magnetic materials such a behavior is known as inverse phase transition.

We investigate the interplay of ferroelectricity and quantum electron transport at the nanoscale in the regime of Coulomb blockade. Ferroelectric polarization in this case is no longer the external parameter but should be self-consistently calculated along with electron hopping probabilities leading to new physical transport phenomena studying in this paper. These phenomena appear mostly due to effective screening of a grain electric field by ferroelectric environment rather than due to polarization dependent tunneling probabilities. At small bias voltages polarization can be switched by a single excess electron in the grain. In this case transport properties of SET exhibit the instability (memory effect).PACS numbers: 72.80.Tm,77.84.Lf Systems with ferroelectric (FE) elements attract much of attention due to their interesting fundamental properties at the nanoscale as well as due to their possible applications in microelectronics, especially in nonvolatile memory devices, in emerging technologies of Terahertz-detecting and in building of advanced (nano)capacitors.1-14 In quantum junctions the ferroelectricity influences electron transport: Tunneling through the FE barriers shows giant electro-resistance effect caused by the strong dependence of electron tunneling probability on the FE polarization and external bias orientations.7,15 Here we focus on the inverse processthe influence of electron transport on ferroelectricity. 2,10The naive guess would be that a single electron, small quantum object, can slightly influence the macroscopic effect -ferroelectricity. However, we show that this is not quite true and discuss the interplay of ferroelectricity and quantum electron transport at the nanoscale in the regime of Coulomb blockade. Polarization in this case is no longer the external parameter but should be self-consistently calculated along with electron hopping probabilities leading to new physical transport phenomena studying in this paper. These phenomena appear mostly due to effective screening of a grain electric field by ferroelectric environment rather than due to polarization dependent tunneling probabilities.Ferroelectrics (FE) are characterized by the polarization P whose direction and magnitude can be changed by applying an external electric field E larger than the ferroelectric switching field, E s . The ground ferroelectric state of a bulk sample is usually not uniformly polarized but divided into domains to lower the electrostatic energy, like in ferromagnets. 16At the nanoscale to influence the polarization of (nano)ferroelectric one can apply strong enough bias to nanotips:2 There is a well developed technique of imaging and control of domain structures in ferroelectric thin films by a tip of a scanning probe microscope, see, e.g., Refs. 2,7,10,[17][18][19] Here we show how ferroelectric polarization switching can be produced by placing a single excess electron at the nanograin. Charged metal particle creates a strong enough electric field, E ≈ 1 MV/cm around it. Numerous ferroelectric (nano)...