Papers by Author: V.V. Ustinov

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Authors: V.V. Ustinov, L.N. Romashev, M.A. Milyaev, T.P. Krinitsina, A.M. Burkhanov
Abstract: The magnetic and magnetoresistive properties of nanostructured Fe/Cr multilayers with ultra-thin Fe layers (the nominal Fe thickness tFe is down to 0.3 Å) have been investigated at low temperatures (down to 2 K) in magnetic fields up to 90 kOe. Nanostructures were MBE grown in ultrahigh vacuum on single crystal MgO substrates. It is shown that Fe layers in nanostructures with tFe < 2 Å are not continuous but consist of separate ferromagnetic clusters. Such cluster-layered nanostructures exhibit superparamagnetic properties and the Kondo-like behavior of resistivity.
Authors: M.A. Milyaev, L.I. Naumova, V.V. Proglyado, T.P. Krinitsina, N.S. Bannikova, V.V. Ustinov
Abstract: The effect of Cr-buffer-layer thickness on the structure, giant magnetoresistance, and coercivity of DC sputtered Cr(tCr)/[Co90Fe10(15Å)/Cu(23Å)]8/Cr(10Å) superlattices has been investigated. A drastic change of hysteresis in a short interval of the buffer layer thickness (15 ÷ 20 Å) has been revealed. It has been shown that in superlattices with low coercivity the (111) texture is present, whereas superlattices without texture demonstrate a large coercivity and high GMR ratio.
Authors: I.D. Lobov, M.M. Kirillova, A.A. Makhnev, L.N. Romashev, V.V. Ustinov
Abstract: The magnetooptical and optical properties, and giant magnetoresistance (GMR) of MBE-grown Fe(tx, Å)/Cr10 Å (tx=0.3-30 Å) superlattices and nanostructured multilayers are studied. The data obtained are used for characterization of magnetic clusters in structures with ultrathin Fe layers (tFe<6.6 Å) and for estimation of interfacial electron scattering parameters in GMR superlattices.
Authors: V.V. Ustinov, L.N. Romashev, M.A. Milyaev, T.P. Krinitsina, A.M. Burkhanov
Abstract: We investigated the structure, magnetic and magnetoresistive properties of antiferromagnetically coupled [Fe(85Å)/Cr(tCr)]12 superlattices with the Cr layers thickness tCr = 12.4 and 13.6 Å, grown simultaneously on (100)MgO and (211)MgO substrates. It is shown that the (211)MgO substrate is appropriate for the growth of (210)Fe/Cr multilayers with a strong uniaxial in-plane anisotropy. The stepwise behavior of magnetization and magnetoresistance is revealed in the case when the magnetic field is applied along the easy axis in a film plane of (211)MgO/[(210)Fe/Cr]12 superlattices. The steps on M(H) and ΔR(H)/R dependences are caused by the flip of the magnetic moments of individual Fe layers. The qualitative information about the sequence of spin-flip transitions is extracted from the comparative analysis of magnetization and magnetoresistance data.
Authors: N.A. Viglin, V.V. Ustinov, T.N. Pavlov, V.M. Tsvelihovskaya
Abstract: A promising idea to use the transport of spin-polarized conduction electrons in a magnetic hetero-structure in order to invert population of the charge-carrier spin level in one of its layers, aiming at creation of an active environment for the electromagnetic radiation amplification, has been realized in a number of FMС/SC structures in which FMС is a ferromagnetic conductor and SC is a semiconductor. The n-InSb single crystals, featured by a high mobility of charge carriers, narrow ESR line, and anomalously high absolute value of the negative g-factor (g = −52), were used as SC. The following materials were used as FMC playing a role of spin polarizer: (i) ferromagnetic semiconductors EuO0.98Gd0.02O and HgCr2Se4, (ii) Geisler alloys Co2MnSn, Ni2MnSn and Co2MnSb. We have demonstrated that the spin-polarized electrons injection into the n-InSb semiconductor from the above-mentioned ferromagnetic materials results in a generation of the laser-type electromagnetic radiation.
Authors: Larisa I. Naumova, M.A. Milyaev, N.G. Bebenin, Tatyana A. Chernyshova, Vyacheslav V. Proglyado, Tatiana P. Krinitsina, Nataly S. Bannikova, Ivan Yu. Kamensky, V.V. Ustinov
Abstract: The dependence of free layer coercivity on the angle between easy axis and applied magnetic field was studied on [Ta, (Ni80Fe20)60Cr40]/ Ni80Fe20/Co90Fe10/Cu/Co90Fe10/Mn75Ir25/Ta spin valves with various interlayer coupling. Sharp decrease on the angle was observed for ferromagnetically coupled spin valves. The coercivity was reduced down to tenth of Oersted without any decrease of GMR-effect by forming nearly parallel anisotropy configuration. The angles at which the transition from hysteretic to anhysteretic magnetic reversal takes place are detected by analyses of the angle dependence of coercivity. Interpretation of experimental data is based on Stoner-Wohlfarth coherent rotation approach.
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