Solid State Phenomena Vol. 190

Abstract: Due to water molecules adsorption the reversible change of domains width and domain structure reconstruction in bismuth-doped ferrite-garnet thin films with perpendicular magnetic anisotropy was observed. The change of domains width was 15% in saturated water vapor at room temperature. The decrease of domains width is explained by the reduction of effective perpendicular magnetic anisotropy constant due to water molecules adsorption.

Abstract: The magnetic susceptibility of Pb1-xCexX (X = S, Se and Te) crystals with several Cerium concentrations ranging from x = 0.006 to 0.036 has been measured between 2 K and 300 K. The experimental susceptibility curves were found to be consistent with a 2F5/2 lowest manifold for Ce3+ ions; the cubic crystal-field splitting values of 2F5/2 were estimated to be about 340 K, 440 K and 540 K for Pb1-xCexTe, Pb1-xCexSe, and Pb1-xCexS, respectively. For all the studied samples, it was found that the 7 doublet lies below the 8 quadruplet. These results confirm that Ce3+ ions substitute Pb2+ in the host crystals. Furthermore, the effective Landé factors were determined by X-band (~9.5 GHz) Electron Paramagnetic Measurements (EPR) to be g = 1.333, 1.364, and 1.402 for Ce ions in PbX, X = S, Se, and Te, respectively.

Abstract: Magnetic properties of a GaAs-based heterostructures containing InGaAs quantum well and 2 nm thick GaAs layer doped with 5 at. % Mn (GaAs:Mn) on flat and vicinal substrates were studied. Two types of ferromagnetism were found. In the heterostructures grown on the flat substrate parallel to the (001) GaAs plane the magnetization obeys the Bloch T^3/2 temperature dependence while for the structures grown on the vicinal surface grown (disoriented by 3°) the magnetization follows percolation dependence.

Abstract: We report on the study of exchange enhancement of g-factor in 2D electron gas in n-type narrow-gap semiconductor heterostructures that feature a strong nonparabolicity of electric subbands. We demonstrate that exchange g-factor enhancement not only shows maxima at odd values of Landau level filling factors but, due to subband nonparabolicity, persists at even filling factor values as well. The magnitude of the exchange enhancement, the amplitude and shape of the g-factor oscillations are governed by both the screening of electron-electron interaction and the Landau level width. The enhanced g-factor values calculated for 2D electron gas in InAs/AlSb quantum well heterostructures are compared with previous experimental magnetotransport data.

Abstract: Temperature dependencies of the Seebeck coefficient, electrical conductivity, heat conductivity and the dimensionless thermoelectric figure of merit ZT of p-Bi₂Te₃, n-Bi₂Se₃ and Sb₂Te₃ doped by Fe or Cr have been investigated in the temperature interval 7 < T < 300 K. At T=4.2 K the Shubnikov-de Haas and Hall effects have been measured. By increasing the Fe content, the hole concentration decreases in p-Bi_2-xFe_xTe₃, while the electron concentration increases in n-Bi_2-xFe_xSe₃. The hole concentration decreases in Sb_2-xCr_xTe₃ with Cr doping. This demonstrates that Fe or Cr act as donors. The Seebeck coefficient increases in p-Bi_2-xFe_xTe₃ and Sb_2-xCr_xTe₃ with increasing Fe or Cr content, while it decreases in n-Bi_2-xFe_xSe₃.

Abstract: Optical and magneto-optical properties of GaMnSb layers fabricated on GaAs (001) substrates by laser ablation technique were studied using spectral ellipsometry (E =1.24-3.25 eV) and the transversal Kerr effect (TKE) (E = 0.5 4.2 eV) as well as atomic and magnetic force microscopy. Spectra of the constituents of the diagonal components of the permittivity tensor as well as TKE depended substantially on the layer fabrication conditions. At room temperature a strong resonant band was observed in the TKE spectra for the GaMnSb layers with low Mn content in the energy range E 0.5-1.5 eV. This resonant TKE band was explained by excitation of surface plasmons in MnSb nanoclusters, which arose during the growth of the layers. In the energy region E >1.5 eV the TKE spectra were related to interband transitions in MnSb inclusions.

Abstract: The galvanomagnetic properties in weak magnetic fields (4.2T300 K, B0.07 T) as well as Shubnikov-de Haas effect (T=4.2 K, B7 T) in the single crystal Pb_1-x-ySn_xV_yTe (x=0.20, y0.01) under hydrostatic compression up to 15 kbar have been investigated. It is shown that under pressure the decrease of activation energy of vanadium deep level, n-p-inversion of the conductivity type at low temperatures and insulator-metal transition take place. In the metallic phase sharp increase of the Hall mobility and appearance of Shubnikov-de Haas oscillations at helium temperature are observed. The pressure coefficient of vanadium level energy is determined and the diagram of the electronic structure rearrangement for Pb_1-x-ySn_xV_yTe under pressure is proposed.

Abstract: A model to describe the influence of longitudinal alternating magnetic field on the nonli-near magnetoimpedance in amorphous wires is proposed. The appearance of even harmonics in the voltage response is shown to arise from the asymmetry in the magnetization reversal process in the wire due to the presence of the longitudinal alternating field. The behavior of even harmonics is analyzed as a function of the external field, alternating field amplitude and current amplitude.

Abstract: The plasmonic system consisting of two-dimensional periodic array of silver cylindrical nanoparticles is considered. The light reflection and transmittance, calculated for various frequencies, show the resonance behavior. Excitation of plasmons in the array of nanorods is studied. The resonance electromagnetic modes are strongly localized around the cylinders and local electric field is much enhanced.

Abstract: Magnetic properties and giant magnetoimpedance (GMI) of CuBe/Fe₂₀Co₆Ni₇₄ electroplated wires was studied for frequency of 1 MHz and the amplitude of the driving current of 20 mA with focus on the development of magnetic field detectors of particular types. The possibility of quantitative ferrofluid concentration measurements was demonstrated. GMI of electroplated wire can be useful for the study of the dynamic properties of the ferrofluid. GMI of the electroplated wires in the non-uniform field created by the permanent magnet was studied in the configuration adapted for automatic control lines, machinery control, and positioning systems.