Solid State Phenomena Vols. 233-234

Abstract: Nano systems with combined magnetic and plasmonic functionalities have become an active topic of research in recent years. By an adequate internal architecture of the constituting components, the magneto-optical activity of these systems can be greatly intensified due to the electromagnetic field enhancement associated with the plasmon resonance. One of such approaches is a creating of magnetoplasmonic crystals (MPlCs) based on the noble and ferromagnetic metals. This work represents results of the investigation of the magneto-optical (MO) properties of the magnetoplasmonic structure, and parameters of the magnetic field sensor based on such structures. Possibility of creation of the magnetic field sensor with different properties is represented.

Abstract: Spectra and field dependencies of Transversal Kerr Effect (TKE) for [(Co₄₅Fe₄₅Zr₁₀)₄₆(Al₂O₃)₅₄(X)/Si (Y)]_n multilayers (ML) with thin layers (X < 2,5 nm; Y < 3,5 nm) have been studied in the energy range 0,5 – 4,0 eV. It was found that TKE field dependencies in the nearest infrared (IR) and visible energy ranges exhibit anomalous behavior. TKE spectra measured in weak (~30 Oe) and strong (~2 kOe) magnetic fields were essentially different. It was shown that magneto-optical response of multilayered structure composite-silicone is the sum of magnetic composite layers and composites formed on interface contributions. And these contributions may have an opposite sign of TKE. Interface magnetic states depend on composite and semiconductor layers’ thicknesses and FM phase concentration in composite layers.

Abstract: The present work has been undertaken to research effects of structure, morphology, volume fraction, spatial arrangement of magnetostrictive intermetallic FeGa alloy particles dispersed in modified polyurethane matrix. Correlation of composite magnetic behavior with structure and mechanical properties has been obtained by measurements of magnetostriction, remanent magnetization anisotropy, SEM, and dynamical mechanical analysis. Anisotropic chain structures of magnetic particles within the polymer with different interparticle interactions were observed. The increase of the magnetostrictive response with tailor-made magnetic anisotropy induced by magnetic particles volume fraction has been demonstrated

Abstract: Magnetic properties, structure and thermal stability of the (Fe_0.7Co_0.3)₈₈Hf₂W₂Mo₂Zr₁B₄Cu₁ alloy ribbon after its nanocrystallization at 620-750°C for 0-20 min in the presence or absence of tensile stresses σ were studied. It was shown that under the effect of tensile stresses a longitudinal magnetic anisotropy with an easy magnetization axis parallel to the long size of the ribbon was induced in the alloy. A better thermal stability of magnetic properties was observed for the alloy subjected to the nanocrystallization annealing at 620° for 20 min with σ = 170 MPa. After the subsequent annealing at 570°C for 25 h without σ, the magnetic properties of the alloy are unchanged. Increasing of the nanocrystallization annealing temperature up to 670-750°C did not result in improvement of the thermal stability of magnetic properties.

Abstract: A new method of intergrain exchange interaction energy determination in nanostructured magnetically hard alloys with spontaneous spin-reorientation transition has been developed and verified. It is based on the knowing of the material magnetic anisotropy constants values at its “easy cone” state and the external negative magnetic field strength H, which reversibly “tears” the exchange coupling between nanograins. It should be more than exchange field and smaller than coercivity value. Using this method the exchange interaction energy parameter for MQP-B+ alloy was estimated. Its value is in agreement with estimated one by FMR technique for film system Fe-Nd₂Fe₁₄B and close to that obtained from the remanent magnetization temperature dependences measurements in negative magnetic fields.

Abstract: We present quantitative evaluation results of micromagnetic structure parameters of nanocrystalline Fe, Fe₉₅Zr₅, Fe₉₀N₁₀, and Fe₈₅Zr₅N₁₀ films obtained by magnetron sputtering. It is shown that quantities of magnetocrystalline K₁, magnetoelastic K_ME, magnetostatic K_MS, and surface K_a,S anisotropies are components of experimentally measured effective local anisotropy K_eff. The shape of the hysteresis loops of the films is determined by the presence of two main macroscopic effective magnetic anisotropies, one of which is the anisotropy field of stochastic domains, and the other is the magnetoelastic anisotropy field due to residual macrostresses.

Abstract: The microstructure and magnetic properties of Fe-Co-Cr alloys with 15 wt % Co were investigated using transmission electron microscopy and magnetic measurements. The secondary decomposition within both the α₂-phase matrix and the α₁-phase particles was observed for magnets subjected thermo-magnetic treatment and subsequent stepped aging or continuous-cooling treatments. During high-temperature treatments (630-600 ^оC), when the α₂ phase is dominant (the volume fraction is more than 50%), the secondary decomposition of this phase takes place (α₂ → α_1' + α_2'). The deterioration of magnetic insulation of α₁-phase particles results in the decrease in the coercive force of alloys. Below 600 ^оC, when the α₁ phase is dominant (the volume fraction is more than 50%), the splitting of elongated α₁-phase particles occurs. When the temperature of stepped-aging decreases in high steps, the secondary decomposition (α₁ → α_1' + α_2') leads to the splitting of initial α₁-phase particles into fine slightly elongated particles and the decrease in the coercive force.

Abstract: The two ways of reducing the dispersion of the demagnetizing fields in magnetic powders of cobalt alloys have been tested: the isolation of magnetic particles in nonmagnetic matrix and compaction of the powders. The ferromagnetic resonance (FMR) and the hysteresis loops of the pretreated magnetic powders were investigated. The FMR linewidth is significantly narrowed both with increasing of the nonmagnetic fraction in the samples prepared by the first way and with increasing of relative density of the compacts. The limit case of FMR linewidth in continuous magnetic film there is no dispersion of the demagnetizing fields is in good agreement with discussed data. The hysteresis loops of powder with the particles coated by the non-magnetic phase became narrow and easy saturated with increasing of nonmagnetic phase fraction.

Abstract: Static magnetic properties, ferromagnetic resonance (FMR) and glancing angle X-ray diffraction spectra (GAXRD) of (CoFeB)/(nonmagnetic interlayer) nanosystems have been studied for three kinds of interlayers: dielectric (SiO₂) and semiconductors (Si and SiC). Matter of discussion is the role of the interlayer material in forming of inner structure of magnetic layers and magnetization curve shape.

Abstract: The magnetic susceptibility dependence on temperature near phase transition point was investigated by theoretical analysis. It is shown that with decreasing of the film thickness the magnetic susceptibility shape curve becomes more rounded finite-size function, centered about the lowered temperature Tc (L). The obtained results are in good agreement with experimental data.