Magnetic properties of some RCo2B2 and RCo4B4 compounds

RCo₂B₂ (R=Pr, Nd, Sm, Gd) and RCo₄B₄ (R=Pr, Nd, Sm) compounds have been investigated by X-ray and magnetometry techniques in the temperature range 4.2-300 K. These compounds crystallize in tetragonal crystal structures of the types CeAl₂Ga₂ and CeCo₄B₄, respectively, with lattice parameters decreasing for increasing atomic weight of the rare earth ion. All compounds order magnetically with the Curie temperatures much below room temperature. Anomalous magnetic behavior is observed for RCo₄B₄ alloys.     

Magnetoelastic waves in ferromagnet plates and films

The explosive development of investigations of magnetization waves in ferrite layers (plates and films) that occurred in recent years resulted in significant deepening and expansion of our conceptions of the effects of the interaction between such magnetization waves and elastic waves. The possibility of synchronization and hybridization of magnetization waves and elastic waves was shown in theory and experimentally for phase velocities of these waves in the direction of propagation along the ferrite layer exceeding the sound speed in the ferrite by one to two orders. At such phase velocities the inhomogeneous exchange energy often turns out to be insubstantial for magnetization wave propagation, and only the dipole energy is substantial. Therefore, we speak substantially about a new kind of magnetoelastic waves, the result of hybridization of pure magnetodipole and elastic waves. Such waves have been designated fast magnetoelastic waves. A brief survey of the theoretical, experimental, and applied investigations of fast magnetoelastic waves is contained in this paper. In the section Theory we present and discuss the fundamental equations, boundary conditions, and approximations necessary for the computation of fast magnetoelastic wave properties and the effects accompanying their propagation. The results of such computations currently known are presented. In the section Experiments we describe the fundamental requirements imposed on the specimens and the measurement methodology to detect and investigate the properties of fast magnetoelastic waves. Results of measurements executed at the present time as well as the prospects for further development in this direction are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 6–23, November, 1988.     

Dielectric properties of pyroactivated SiO2 films

The physical properties of SiO₂ films obtained by pyrolytic decomposition of tetraethoxysilane vapor in an inert medium using activating ultraviolet radiation are analyzed. The mechanisms of current flow in Me-SiO₂-Me systems are discussed on the basis of qualitative ideas concerning the nature of the conductivity in amorphous dielectrics, when there is a complex trap spectrum and reversible temperature changes present in the film structure.     

Determination of optical properties of SnO2 films

Summary The optical properties of conductive transparent thin films of undoped SnO₂, prepared by using magnetron supttering, were studied by measuring the transmittance and the reflectance between λ=0.25 μm and λ=3μm. The extracted optical constants are interpreted to give values of a direct band gap of the order of 4 eV and of an indirect band gap of the order of 3 eV. Typical SnO₂ films transmit ≈85% of visible light, have sheet resistanceR _∂ (100÷800) Ω_∂ and resistivities of (2.4·10⁻³÷1.8·10⁻²) Ω cm.

---

Riassunto Mediante la misura dei valori di transmittanza e di riflettanza per lunghezze d'onda comprese fra 0.25 μm e 3 μm, sono state studiate le proprietà ottiche di film sottili (trasparenti e conduttivi) di SnO₂ non drogato, preparati mediante sputtering. Dai valori così ottenuti sono stati ricavati valori del gap diretto dell'ordine di 4 eV e di quello indiretto dell'ordine di 3 eV. Un film di SnO₂ presenta tipicamente valori della transmittanza intorno all'85%, per luce visibile,R _∂ intorno ai (100÷800) Ω_∂ e resistività fra 2.4·10⁻³ e 1.8·10⁻² Ω cm.

---

Резюме Пзмеряя величины пропускания и отражения в области длин волн между λ=0.25 мкм и λ=3 мкм, исследуются оптические свойства проводящих прозрачных тонких пленок нелегированного SnO₂, приготовленных с помощью напыления. Из полученных оптических постоянных извлекаются значения прямой щели, порядка 4 эВ, и непрямой щели, порядка 3 эВ. Типичные пленки SnO₂ пропускают ∼85% видимого света, имеют сопротивлениеR _∂ (100÷800) Ω_∂ и удельные сопротивления в области (2.4·10⁻³÷1.8·10⁻²) Ом·см.

     

纳米晶氧化锡薄膜的接触特性

在 Ar和 O2 气体中 ,基片温度在 15 0～ 40 0℃的条件下 ,用直流磁控溅射的方法可以制备纳米晶透明导电薄膜。实验利用 TL M模型测试了纳米晶 Sn O2 透明导电薄膜的方块电阻、单位面积薄膜的接触电阻和电极与薄膜的结合力随热处理温度的变化情况     

Transferred hyperfine interactions in ferrimagnetic RCo2 cubic Laves phase compounds

The ferrimagnetic system (Gd_xY_1−x)Co₂ has been studied by the Mössbauer effect of ¹⁵⁵Gd and by the NMR of ¹⁶⁵Ho as a substitutional impurity. The data are interpreted in terms of a simple model which involves transferred hyperfine fields from the lanthanide and cobalt ions and which allows for crystal field quenching of the holmium moment.     

Dielectric properties of Sb2O3 films

A study has been made of the dielectric constant, dielectric loss, electrical conductivity in weak and strong fields, and the dielectric strength of polycrystalline Sb₂O₃ films produced by vacuum evaporation. Electronic polarization is shown to dominate in these films. The nonlinear voltage dependence of the current in strong fields is easily explainable in terms of a Frenkel mechanism for electrostatic ionization. The film breakdown is due to impact ionization of impurities and the formation of a shower.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol. 12, No. 5, pp. 52–55, May, 1969.     

Structural and galvanomagnetic properties of CuInS2 films

Thin copper-indium-disulphide films were prepared by thermal evaporation technique. X-ray diffraction analysis of the compound used for evaporation showed a tetragonal polycrystalline structure. Differential Thermal Analysis (DTA) of this compound showed two exothermic peaks at 585 and 632 °C. Thin films with thicknesses of 0.14 and 0.27 nm have a deposition rate 10 nm/min, while those with thicknesses of 0.54 and 0.56 nm have a deposition rate 48 nm/min. The obtained films have polycrystalline structure as shown from the electron diffraction study. A growth process was detected in the films by transmission electron microscopy as the film thickness increases. The surface topography was revealed by scanning electron microscopy. The variations of Hall mobility and carrier concentration with magnetic induction were studied. The resistivity-temperature relationship was investigated, from which the activation energies before and after annealing were found to be 0.2, 0.3 and 0.055 eV, respectively.     

Ethanol sensing properties of SnO2 thin films

Tin dioxide thin films have been deposited on alumina substrates by different methods in order to test their reliability as a breath analyser. Despite the obvious simplicity of spray pyrolysis, both the structural and electrical properties of the films thus prepared were strongly dependent to the deposition conditions. The samples exhibited poor crystallinity and porous microstructure. They were sensitive to ethanol vapour but since the resistance of the samples reached several MΩ, antimony doping was performed to fit a more convenient detection range. An alternative method was then used to prepare tin dioxyde thin films by evaporation of metallic tin followed by thermal oxidation. In this case, grain size was enhanced up to 100 nm but films remained highly porous. The ethanol sensitivity of evaporated samples was determined. In order to study more accurately the influence of microstructure on sensing ability, dense thin films were prepared using a CVD method with tetrabutyl tin as precursor. Preliminary results indicated that films with different crystallite sizes could be grown by varying the deposition temperature. Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995     

Preparation and properties of epitaxial ZnGeP2 films

Thermodynamic analysis has been applied to the vapor over a ZnGeP₂ crystal when the chlorine source is provided by ZnCl₂. ZnGeP₂ film growth has been examined and the electrophysical and photoluminescence parameters have been measured. All these autoepitaxial films have the chalcopyrite structure, while those parameters are determined by the defects and the substrate orientation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 74–78, April, 1988.We are indebted to L. G. Lavrent'eva for interest, to A. I. Gribenyukov and T. E. Tkachenko for assistance in growing the single crystal; and to F. Kim for the microprobe analysis.     

ESR study of Gd and Nd in RNi2 and RCo2 laves phase compounds

We report ESR study of Gd and Nd in RCo₂ and RNi₂ (R = Sc, Y, Zr, Lu, Ce) compounds. The variation of the Gd g shift from RCo₂ to RNi₂ compounds is consistent with a recent calculation of the density of states and also with the systematic behaviour demonstrated previously by us for transition metal intermetallic compounds. The Nd resonance in CeNi₂ and LuNi₂ indicate Γ₆ ground state crystalline field splitting; the Nd g value in YNi₂:Nd and LuNi₂: Nd is anomallous. Several possibilities for this anomally are discussed.     

Investigation of optical properties of thin CuGaTe2 films

Thin films of copper tellurogallate were obtained by the method of pulsed laser spraying. The structure of the films and the parameters of the unit cell were determined by the x-ray method. It is shown that the films possess p-type conduction and their resistivity decreases with an increase in the substrate temperature. From the transmission near the edge of the fundamental absorption band a determination was made of the energy of interband transitions, crystalline cleavage, and spin-orbital splitting. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 946–949, November–December, 1998.     

Electrical properties of flash-evaporated V2O5 films

Electrical properties of vanadium-pentoxide flash-evaporated films are reported. Transport parameters are investigated as functions of growth conditions and post-deposition treatments. The conduction mechanism is analyzed using the small polaron hopping model. The main features of the electrical conductivity such as the polaron hopping energy, the disorder energy term and the density of states are determined. Paper presented at 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

Electrical properties of CdF2 films

The electrical conduction at room temperature is examined in CdF₂ films between 200 and 2000 Å thick. The current response is studied, and two conductivity states alternating with a memory switching condition are obtained. The current is attributed, at least in part, to ionic transport.