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Purpose. By a method of ion-beam sputtering of two targets (one of the CoFeB alloy, the second of TiO2 on a rotating glass-substrate substrate, a series of samples were obtained with a gradient of the composition and thickness of the composite (Co40Fe40B20)x(TiO2)1–x on the diffraction patterns of amorphous composites, a halo was found corresponding to the average interatomic distance close in magnitude to the interplanar spacing of the most intense diffraction lines in CoFe alloys. Results. Using IR spectroscopy, the modes were identifi ed that correspond to interatomic bonds in amorphous composites (CoFeB)x (TiO2)1–x of various compositions. The presence of bonds with oxygen of all elements of the composite Fe – O, Co – O, Ti – O, B – O, as well as the formation of intermediate chemical bonds Ti – O – B and Ti – O – Co between the atoms of the dielectric and metal components of the composite has been established. Conclusions. Based on the data obtained, a model of amorphous composites (Co40Fe40B20)x(TiO2)1–x is proposed, in which metal particles are represented as a nucleus of metal CoFe clusters with a shell of d-metals oxides and borides/oxyborides distributed in a dielectric matrix of titanium dioxide TiO2–x.

The aim of this work was to comprehensively study the effect of the variable atomic composition and structural-phase state of Cox(MgF2)100-x nanocomposites on their nonlinear transport and magnetic/magneto-optical properties. Micrometer-thick nanocomposite layers on glass substrates were obtained by means of ion-beam sputtering of a composite target in the argon atmosphere in a wide range of compositions (x = 16–59 at.%). Using a low metal content in the nanocomposite, magnesium fluoride was kept in the nanocrystalline state. As the metal content increased, nanocrystalline cobalt was formed. The value of the resistive percolation threshold, xper = 37 at.%, determined from the concentration dependences of the electrical resistance of the nanocomposites coincided with the beginning of nucleation of the metallic nanocrystals in the MgF2 dielectric matrix. The absolute value of the maximum negative magnetoresistive effect in the nanocomposites was 5% in a magnetic field of 5.5 kG at a Co concentration of x = 27 at.%. [ABSTRACT FROM AUTHOR]

We present results of experimental studies of magnetic properties, resistivity and magnetoresistance (MR) of (Co84Nb14Ta2)x(Al2O3)100-x films deposited onto a glass-ceramic substrate by the ion-beam sputtering, focusing on MR in high magnetic fields for compositions close to the percolation threshold (x=47-57 at.%). The samples consist on Co-Nb-Ta metallic nanogranules size of 2-5 nm which are embedded into the non-stoichiometric Al-O matrix. Magnetization was measured by SQUID magnetometer at T=4.2-350 K. MR was studied in the pulsed magnetic fields μ0H up to 20 T at T=70-300 K in three geometries: magnetic field in plane parallel and perpendicular to current, magnetic field perpendicular to plane. The pulse duration was 11-12 ms. For the sample with x=57 at.% the temperature dependence of conductivity follows the lnT behavior that matches a strong tunnel coupling between nanogranules. With decreasing metal volume fraction lnT behavior gradually changes to the T1/2 dependence at 47 at.%. For all samples MR is small (

The spectral and field dependences of the Transversal Kerr Effect (TKE) for (Co40Fe40B20)Z(SiO2)100-Z/Si (or С) multilayer (ML) nanocomposite-semiconductor structures were studied depending on the concentration of the nanocomposite layer ferromagnetic phase (Z), chemical of semiconductor layer and its thickness. It was found that under certain conditions an addition of thin nonmagnetic semiconductor layer leads to the increase of a multilayer magneto-optical (MO) response and softening of the magnetic properties of ML structure, up to the appearance of ferromagnetic (FM) ordering. The observed anomalous changes in magnetic and MO properties are well correlated with abrupt changes in the electric properties of ML structures. Decreasing of ferromagnetic phase concentration Z in the nanocomposite layer as well as increasing of the semiconductor layer thickness led to the disappearance of anomalous behavior in the MO properties. The results obtained are discussed taking into account the formation of a new magnetic phase on the FM granule-semiconductor interface.

We investigated the role of microstructure and In2O3/C interlayer thickness on the electrical transport properties of [(Co40Fe40B20)34(SiO2)66/(In2O3)/C]46 multilayers prepared using ion-beam sputtering. These multilayers were characterized using an X-ray diffraction, X-ray reflectivity, impedance spectroscopy, and magnetoresistive measurements. The X-ray diffraction data showed that regardless of the layer thickness, all components of the multilayers are X-ray amorphous. Fitting X-ray reflectivity data, multilayer periodicities are extracted and layers thicknesses, densities and roughnesses are determined. Impedance spectroscopy has shown a resistive-capacitive coupling between electrically conductive ferromagnetic CoFeB clusters which corresponds to the model of a prepercolation composite. For the thinnest multilayer with nonmagnetic In2O3/C interlayer thickness of about 1.6 nm, we managed to achieve a magnetoresistance of about 0.8% at room temperature and 3.2% at cryogenic temperature. [ABSTRACT FROM AUTHOR]

The multilayer nanostructures have drawn attention in fields from spintronics to microwave electronics. The purpose of this work was to determine the composition of individual layers and to control interfaces in three‐layer superstructures [(Co40Fe40B20)34(SiO2)66/ZnO/C]46 by means of X‐ray diffraction and X‐ray reflectivity. The samples with different thicknesses of metal‐containing composite layers together with zinc oxide and carbon interlayers were deposited on the glass substrate by ion‐beam sputtering of three targets, one of which was a composite (Co40Fe40B20)34(SiO2)66. X‐ray diffraction results showed the X‐ray amorphous state of the ferromagnetic metal clusters CoFeB, the dielectric matrix of silicon oxide SiO2, and carbon interlayers. However, the intermediate layers of the zinc oxide ZnO were found to have a nanocrystalline structure. The X‐ray reflectivity measurements indicate a good agreement between the experimental and nominal values of both the periods of three‐layer superstructures and the thicknesses of metal‐containing composite layers and interlayers. [ABSTRACT FROM AUTHOR]

Thermal stability of the multilayer (Mg/NbOx)82 nanostructure and the effect of heat treatment on its electrical properties and phase composition depending on the bilayer thickness are studied. The studied (Mg/NbOx)82 samples contain 82 bilayers whose thickness varies in the range from 2.2 to 6.2 nm. The NbOx layer thickness in the multilayers is the same (0.96 nm) in all samples, while the magnesium layers thickness is varied. It is established that the magnesium layers are either discrete (a set of nanosized particles) or continuous depending on their thickness. A metallothermic reaction occurs in (Mg/NbOx)82 multilayer nanostructures at a temperature of 430 °C: niobium oxide decomposes and the released oxygen partly oxidizes the magnesium layers. That leads to the conductive magnesium metal layers breaking and to the sharp increase of the nanostructures’ resistance by more than two orders. Despite the metallothermic reaction, the layering of the (Mg/NbOx)82 nanostructures as a whole and the presence of unoxidized magnesium inclusions remain even after heating up to 450 °C. [ABSTRACT FROM AUTHOR]

Interatomic interactions and superstructures of multilayer nanostructures (MLNS) consisting of ferromagnetic composite layers and silicon interlayers with or without hydrogen are studied here by means of X-ray diffraction (XRD), X-ray reflectivity (XRR), IR spectroscopy, and ultra-soft X-ray emission spectroscopy (USXES). The MLNS [(Co45Fe45Zr10)35(Al2O3)65/a-Si:H]100 and [(Co45Fe45Zr10)35(Al2O3)65/a-Si]120 were deposited on the substrate Si(100) by ion-beam sputtering of two targets, where the first target was a plate of Co45Fe45Zr10 alloy with Al2O3 inserts, and the second target was a single-crystal silicon. Our results show that the iron (FeSi2) and cobalt (CoSi, CoSi2) silicides are formed at the interfaces of the composite metal-containing layer/silicon interlayer. It is demonstrated that the metal clusters of composite layers and interface silicides are partially oxidized to form iron, cobalt, and silicon oxides together with zirconium silicate. Due to the formation of silicides at the interfaces, the composition of MLNS superstructures becomes more complex, and their periods are significantly reduced (down to 5–6 nm) compared to the nominal values of bilayers of about 6.9 nm. [ABSTRACT FROM AUTHOR]