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Vol 87, No 3 (2023)
Articles
Domain wall drift in single crystal plates with complex magnetic anisotropy
Abstract
Numerical 2D simulating of static and dynamic structures of magnetic domain walls in a thick single-crystal plate-(111) with crystalline cubic and induced uniaxial magnetic anisotropy was performed. The domain wall drift in a low-frequency harmonic magnetic field was established, and the dynamic deformation of domain wall structure was revealed.
310-314
Spectra of the effects of magnetic birefringence and dichroism in magnetic colloids with different particle sizes
Abstract
Experimental studies of the spectral dependences of the effects of birefringence and dichroism in magnetic colloids with magnetite nanoparticles with an average size of 5.5 and 8 nm have been carried out. It is shown that the magnitude of the effects in a sample with larger particles is approximately two times greater at the same volume concentration. Possible reasons for this difference are analyzed, considering the polydispersity of the samples, as well as the possibility of the presence of magnetically hard and superparamagnetic particles in them. The calculations of the spectra of the effects of birefringence and dichroism showed good agreement with the experimental data.
315-320
Application of various influences to obtain isolated or oriented nanoparticles
Abstract
Heterostructural nanowires with alternating copper and nickel layers were obtained by matrix synthesis, then were cut into cylindrical magnetic nanoparticles of calibrated sizes. For their use in medicine, the tasks of their separation (overcoming agglomeration) and spatial orientation for targeted drug delivery and hyperthermia, respectively, were solved.
321-327
Magneto-optical spectroscopy of GaSb–MnSb composites
Abstract
Polycrystalline samples of (GaSb)100 – x(MnSb)x composites with x = 69.2, 52.0 and 31.7 mol %, MnSb, Mn2Sb compounds were synthesized and their magneto-optical properties in the equatorial (transverse) Kerr effect geometry were studied. The difference of magneto-optical spectra for related compounds MnSb and Mn2Sb is shown. The anomalous temperature behavior of the magneto-optical signal in the composites and MnSb with decreasing temperature is associated with a redistribution of the population of d-states with the opposite spin index.
328-332
Investigation of the effect of temperature on the magneto-optical effect of changing the transparency of a magnetic emulsion
Abstract
The influence of temperature on the effect of changes in the transparency of magnetic emulsions with low interfacial tension in a magnetic field has been studied. A nonmonotonic dependence of the amplitude of the magneto-optical effect with a change in the temperature of the test sample is found.
333-337
Features of thermal expansion in substitution alloys based on heavy rare-earth metals \({\mathbf{R}}_{{{\mathbf{1}} - x}}^{{\mathbf{I}}}{\mathbf{R}}_{x}^{{{\mathbf{II}}}}{\mathbf{F}}{{{\mathbf{e}}}_{{\mathbf{2}}}}\)
Abstract
We consider the features of the behavior of thermal expansion and magnetostriction in magnetically ordered substitutive alloys based on heavy rare earth metals, namely: TbFe2, Tb0.8Zr0.2Fe2, Tb0.8Sm0.2Fe2 and Gd0.8Sm0.2Fe2. It is found that the of thermal expansion anomalies observed in alloys are mainly due to the competition of exchange interactions. In TbFe2 and Tb0.8Zr0.2Fe2 alloys invar-type features are observed in a wide temperature range.
338-342
Dynamics of multiphase magnetic fluid systems in microchannels of different shapes in a nonhomogeneous magnetic field
Abstract
We presented the results of a study of the dynamics of gas bubbles injected into a ferrofluid under the influence of an inhomogeneous magnetic field in microchannels of five configurations. The dependences of bubble sizes on the configuration of the magnetic field and the physical properties of the magnetic fluid are obtained. The results obtained can be used in gas meters and dispensers in microfluidics.
343-347
Effect of the magnetic field configuration on the detachment of gas bubbles in a magnetic fluid
Abstract
The process of detachment of gas bubbles in a vertical channel filled with a magnetic fluid from a gas cavity in uniform magnetic field is studied. The behavior of the air–magnetic fluid interface now of separation is considered and dependences of the size of the detached bubbles on the configuration of the magnetic field, concentration of the magnetic fluid, and channel thickness are shown.
348-352
Materials based on RCo2 and RMnSi for solid-state magnetic cooling
Abstract
The aim of the work was to create highly efficient materials for solid-state magnetic cooling at temperatures below room temperature (120–280 K). For this, new (R,R')(Co,T)2 and R(Mn,T)Si (T = Fe, Co, Al) compounds with a noticeable magnetocaloric effect (MCE) in the Curie temperature region were investigated. The main regularities of the behavior of the MCE depending on the composition are revealed.
353-358
Dynamics of the magnetization vector of the spin-valve free layer with planar anisotropy under the action of magnetic fields of the arbitrary direction
Abstract
The dynamics of the magnetization vector of the free layer of the spin-valve structure with planar layers anisotropy is simulated in the magnetic fields of the arbitrary direction. The bifurcation analysis of the dynamical system made it possible to determine the conditions of the changing singular points type and classify the magnetization dynamics by types.
359-367
Formation of skyrmions in thin CoPt films with an atomic force microscope probe
Abstract
Methods of magnetic force microscopy have been developed that make it possible to visualize the evolution of the domain structure when scanning a sample with a magnetic probe. These methods were used to study the processes of formation of skyrmions in thin CoPt films, a characteristic feature of which is the presence of the Dzyaloshinskii–Moriya interaction. A change in the position, shape, and size of skyrmions under the action of a spatially inhomogeneous magnetic field of the probe has been experimentally demonstrated.
368-372
The magnetostriction in garnet ferrite Y1.8Bi1.2Fe3.5Ga1.5O12 synthesizing by the modified method of gel combustion using ethylene glycol
Abstract
The temperature dependence of the magnetostriction constant of yttrium–bismuth iron garnet with Fe3+ ions replaced by Ga3+ has been studied. The description of the improved technology for the synthesis of bulk samples, the results of X-ray diffraction analysis and the study of the microstructure are given. A change in the sign of the magnetostriction constant versus temperature, which is associated with a spin-orientation transition, is found.
373-376
Magnetic and dielectric properties double perovskite Sr2MnTiO5.87
Abstract
Magnetic and dielectric properties of Sr2MnTiO5.87 double perovskite have been studied. Magnetic phase transitions were observed at 12 and 43 K in the FC and ZFC curves of magnetization and magnetic heat capacity, the nature of which is being discussed. From the analysis of the lattice contribution to the specific heat, the Debye and Einstein temperatures were determined, which were θD = 217 К, θЕ1 = 275 К, θЕ2 = 615 К, θЕ3 = 2000 К.
377-382
The influence of magnetic film anisotropy on the frequency-modulated signal detection
Abstract
We studied the possibility of using a magnetostriction converter for detecting a microwave signal with frequency modulation. The magnetization vector and elastic displacement oscillations in a normally magnetized ferrite film with crystallographic anisotropy are considered. We analyzed the effect of crystallographic cell orientation on the nature of the magnetization dynamics and elastic displacement oscillations, the establishment of various oscillation modes, and the detection process.
383-389
Adsorption of organic dyes by Fe3O4@C, Fe3O4@C@C, Fe3O4@SiO2 magnetic nanoparticles
Abstract
The Fe3O4@C, Fe3O4@C@C, and Fe3O4@SiO2 core-shell nanoparticles were synthesized using thermal decomposition and co-precipitation techniques and characterized by X-ray spectroscopy, transmission electron microscopy and magnetometry. It is shown that the magnetic core of all nanoparticles is nanocrystalline with crystal parameters corresponding to only one Fe3O4 phase, which is covered with a uniform shell of amorphous carbon or silicon oxide about 8 nm thick. The main attention was paid to the adsorption properties of nanoparticles with respect to four dyes: methylene blue, Congo red, eosin Y, and rhodamine C. The high selectivity of Fe3O4@C nanoparticles with respect to various dyes was revealed.
390-395
Competitive effects of substitutions in La1 – xSrxMn0.9(MgyGez)0.1O3 + γ system
Abstract
Structural, magnetic, and electrical characteristics of La1 – xSrxMn0.90(Mg0.5Ge0.5)0.10O3 + γ (0.15 < x < 0.30, γ = 0, γ > 0) and La0.91Sr0.09Mn0.90Mg0.10O3, La0.71Sr0.29Mn0.90Ge0.10O3 manganites are investigated and compared. Comparison of the properties of manganites having identical summary concentrations of substituents for manganese and equivalent concentrations of Mn4+, Mn3+ ions revealed several competing effects caused by Sr2+(4p6), Mg2+(2p6), Ge4+(3d10) ions and oxygen.
396-401
Liquid-crystal composites of carbon nanotubes in a magnetic field: bridging from the molecular-statistical model to phenomenological theory
Abstract
Based on the thermodynamic potential of the molecular-statistical mean-field theory of liquid-crystal composites of carbon nanotubes, a representation of the free energy in the form of the Landau expansion is obtained. The resulting expansion is compared with the previously proposed phenomenological theories.
402-407
Macroscopic helicity of a suspension of chiral magnetic particles based on nematic liquid crystal
Abstract
The basic state of a suspension of chiral ferroparticles based on a nematic liquid crystal is studied when the finite coupling between the impurity and liquid crystal subsystems is considered. An additional contribution to the free energy functional due to the chiral shape of impurity particles, which describes the formation of spontaneous macroscopic helicity of the orientational structure of a nematic liquid crystal, is proposed.
408-411
The role of manganese substitutions of iron cathiones in changes of magnetic and electrical characteristics of BiFe1 – xMnxO3 magnetoelectrics (x = 0.05 and 0.15)
Abstract
The samples of BiFe1 – xMnxO3 solid solution system (x = 0.05 and 0.15) are ferromagnetics and semiconductors unlike BiFeO3. Growth of x leads to a decrease in Curie temperature (TC = 605 K for x = 0.05 and 550 K for x = 0.15) and growth of dielectric permittivity ε at room temperature. The decrease in the value of specific magnetization with increasing x is due to the redistribution of the volumes of ferromagnetic and antiferromagnetic phases.
412-416
Control of spin wave propagation modes in the yttrium iron garnet waveguide by means of local laser heating
Abstract
The results of micromagnetic modeling of the magnetic structure on the surface of a film of yttrium iron garnet (YIG) are presented, where a region of altered saturation magnetization was created by focused laser radiation. Based on the constructed amplitude-frequency characteristics of signal transmission through a magnon structure with a heating region, the possibility of implementing spin-wave signal filtering modes with a change in the diameter of the heated region on the YIG surface is shown.
417-421
Magnetic and elastic oscillations in manganese-zinc spinel crystal in the region of spin reorientation
Abstract
The formula for the magnetic dissipation parameter of ferrimagnetic crystals depending on the constant magnetic field and the anisotropy field was obtained. It was shown that in the region of magnetic reorientation in a manganese-zinc spinel crystal, magnetic and elastic vibrations of infinitely small amplitude and low frequency are excited, which are characterized by giant damping in a wide temperature range.
422-428
Growth and electron transport characteristics of epitaxial thin strontium iridate films
Abstract
The results of a study of epitaxial thin films of strontium iridate with the compositions Sr2IrO4 and SrIrO3 obtained by laser ablation and direct current cathode sputtering, respectively, are presented. Data on the growth technology, crystal structure, electrophysical parameters are given, and the activation energy for low-defect dielectric Sr2IrO4 films is calculated.
429-433
Pinning of vortices during the passage of turbulent magnetization reversal waves in antidot films with through and non-through holes
Abstract
Micromagnetic modeling of the process of magnetization reversal in films with antidot arrays, initiated by a moving domain wall, is performed. Under certain conditions, a narrow magnetization reversal zone appears, filled with vortex structures (turbulent wave). Changes in speed, temporary or final stops of the wave are observed. The existence of a connection between the features of wave motion and the structure of the vortex zone is shown.
434-440
Structure and FMR characteristics of magnetic composite films (CoFeB + SiO2)
Abstract
Composite films (FeCoB + SiO2) with a low metal alloy concentration x < 0.35 have a small spread of film surface elevations. At large x > 0.53, a greater scatter of elevations and their smooth distribution in the films are observed. The concentration dependence of the FMR linewidth exhibits a maximum at x = 0.45, which is related to the percolation structure in the films.
441-445
Aging effects in critical behavior of Heisenberg anisotropic ultrathin films
Abstract
We present the results of Monte-Carlo studies of the non-equilibrium properties of ferromagnetic Heisenberg films. Aging effects were observed in non-equilibrium critical behavior. The calculations were carried out for both high-temperature and low-temperature initial states. The characteristic correlation time, which diverges at the transition temperature in the thermodynamic limit, was obtained as a function of system size and waiting time.
446-449
Ferromagnetism and two magnetic phases in rutile (TiO2) implanted with cobalt ions: effect of substrate temperature and orientation
Abstract
Room-temperature ferromagnetism and two magnetic phases: cobalt metal nanoparticles and a solid solution of divalent cobalt ions have been observed in single-crystal rutile (TiO2) implanted with cobalt ions to high dose level. Here we present the results of our structural and magnetic studies showing an influence both the temperature and the orientation of TiO2 substrate during a cobalt ion implantation, as well the effect of post-implantation thermal annealing (in air or in vacuum) on ferromagnetism value and magnetic phase composition of Co-implanted rutile.
450-456