Vol 163, No 1 (2023)

We have constructed a theory of the Hall effect appearing during the passage of current in a magnetic tunnel junction due to the spin–orbit interaction in an insulator barrier in the approximation of a delta-shaped barrier potential. Both the normal Hall current flowing in metal banks as a result of asymmetric scattering in the tunneling barrier and the anomalous current existing only in the tunneling barrier due to the presence of the spin–orbit interaction in it are taken into account. We have considered the Rashba interaction that can be of intrinsic origin (noncentrosymmetric form of the barrier) or can be induced by an extraneous electric field emerging as a result of application of a potential difference to the barrier. Such a field can reach a value on the order of 109 W/m, which is close to intrinsic atomic fields. The Hall current has both linear and quadratic components in the voltage applied to the tunnel junction. The existence of the nonlinear Hall voltage corresponding to it has been illustrated experimentally in a CoFeB/MgO/Pt tunnel junction, in which the transverse (Hall) voltage has been measured in the Pt layer.

Copper oxyborate single crystals with a ludwigite structure, Cu2MBO5 (M = Cr, Fe, Mn), containing different substitutes in the trivalent subsystem have been grown from Bi2O3–MoO3–Na2O–B2O3 fluxes. The structural properties of grown compounds have been compared in detail using X-ray diffraction and Raman spectroscopy methods. In addition, these methods have been used to determine the degree of cationic ordering in these ludwigites. The temperature and field dependences of the Cu2MBO5 (M = Cr, Fe, Mn) ludwigite magnetization are presented.

The magnetic properties of the surface layer of an epitaxial bismuth-doped iron garnet film with a weak uniaxial anisotropy are studied by magnetic force, optical, and nonlinear optical microscopy. A significant modulation of optical second harmonic generation intensity along stripe domains is detected near the free film surface. This modulation is caused by periodic distortions of the stripe domain structure near the film surface and the presence of surface closure domains detected by magnetic force microscopy (MFM). A series of MFM images of the film taken in an in-plane magnetic field varying from –400 to 400 Oe demonstrates quasi-static nucleation of closure domains periodically located along stripe domains.

We study the structural, magnetic, and optical properties of double manganites LnBaMn2O6 with Ln = Pr, Nd, Sm, Nd1 – xSmx (x = 0.25, 0.5, 0.75). Analysis of the temperature dependences of transmission in the near IR range has shown the difference in the responses of the charge subsystem for different types of charge/orbital ordering in the system. In PrBaMn2O6 manganite, the orbital ordering of the dx2−y2 type leads to an insulator state at low temperatures. The charge subsystem of manganites NdBaMn2O6, Nd0.75Sm0.25BaMn2O6, and Nd0.5Sm0.5BaMn2O6 is sensitive to the orbital ordering type: in the temperature interval TCO2 < T < TCO1, where pairwise alignment of layers with d3x2−r2/d3y2−r2 ordered orbitals is realized, the semiconductor character of charge carriers is observed, while upon a transition to the layer-by-layer alignment of orbitally ordered layers for T < TCO2, charge carriers are of the metal character. In manganites Nd0.25Sm0.75BaMn2O6 and SmBaMn2O6, the absence of clearly manifested metal nature of the charge subsystem at T < TCO2 is associated with the formation of the antiferromagnetic ordering of the CE type.

Using experimental and numerical investigation, we demonstrate laser-controlled propagation and interaction of spin waves in an irregular magnetic structure in the geometry of the Mach–Zehnder interferometer. It is shown that the use of laser radiation for heating one of the interferometer arms leads to controlled interference of a spin-wave signal in the output section. The yttrium–iron garnet film heating under the action of laser radiation is measured experimentally. Using micromagnetic modeling, the evolution of the spin-wave interference pattern under the action of laser heating of one of the interferometer arm is demonstrated. The results of this study ensure a simple solution for developing tunable spin-wave interferometers for the paradigm of the magnonic logics.

This paper is devoted to a theoretical study of the magnetic properties of an ensemble of single-domain interacting magnetic nanoparticles embedded in an immobile polymer matrix. This model is typical for the description of magnetically active polymer ferrocomposites widely used in industrial and biomedical applications. A ferrocomposite is assumed to be produced by carrier medium solidification in a ferrofluid in an external magnetic field hp at a polymerization temperature Tp; after carrier fluid solidification, the nanoparticles retain the spatial distribution and orientation of their easy magnetization axes that they had before carrier medium solidification. The contribution of interparticle dipole–dipole interactions to the static magnetization of a ferrocomposite as a function of the magnetic field strength h and polymerization field hp has been studied separately. The effects of the polymerization temperature and the size of magnetic nanoparticles on the magnetic properties of a ferrocomposite have been analyzed. The analytical expressions for the magnetization and initial magnetic susceptibility presented in the paper make it possible to predict the magnetic properties of a ferrocomposite as a function of its intrinsic characteristics and synthesis conditions, which is a theoretical basis for the production of ferrocomposites with a predetermined magnetic response in a given magnetic field.

The synthesis and the structural and magnetic characteristics of ternary nonstoichiometric Fe65 – xAl35 – yMx, y (My = Ga, B, Sn; Mx = V, Mn; x = 3, 5, 10 at %) compounds are experimentally and theoretically studied. Quantum-mechanical calculations of the energy of formation and an electronic structure explain the characteristic features of the phase transformations that occur during the synthesis and describe the experimentally observed changes in the magnetic parameters for various impurity elements.

A meander waveguide made of an yttrium iron garnet (YIG) film with variation of the profile is studied with a view to the possible control of band bands for surface spin waves (SSWs). The finite element method is used to determine the control mechanism of forbidden band gaps in thin YIG films. The electromagnetic problem is solved, and the dispersion characteristics of spin waves are plotted for various geometrical parameters of the meander. The nature of the change in the frequency ranges of Bragg forbidden band gaps is studied in detail depending on the profile of the meander. It is demonstrated that a three-dimensional spin-wave structure with broken translational symmetry that uses vertical spin-wave transport provides an information signal transmission in a three-dimensional configuration of magnonic networks.