Dependence of the microstructure and magnetic properties of amorphous TbFeCo films on the type and pressure of the gas in sputtering

Amorphous Tb₃₀Fe₆₀Co₁₀ films have been fabricated by magnetron sputtering. The dependences of the microstructure and magnetic properties of these films on the type and pressure of the gas in the sputtering chamber have been studied. The pressure of the Ar, Kr, and Xe gases used in the experiments is varied in the sputtering chamber from 0.01 to 4.00 Pa. It has been established that sputtering in the heavy gas (Kr) conducted within the pressure range covered does not permit fabricating TbFeCo films with the easy magnetization axis perpendicular to the film plane. With Xe used at pressures below 1.0 Pa, one observes in TbFeCo films an increase of the coercivity, with the hysteresis loop approaching rectangular shape. Sputtering and deposition in Ar at a pressure of ??0.67 Pa result in the formation of amorphous Tb₃₀Fe₆₀Co₁₀ films with magnetic characteristics satisfying the requirements imposed upon information carriers intended to be employed in perpendicular recording. It has been demonstrated that, by magnetron sputtering in an Ar atmosphere performed at pressures below 1 Pa, one can produce amorphous Tb₃₀Fe₆₀Co₁₀ films suitable for magneto-optical ultra-high-density information recording.     

TiN underlayer and overlayer for TbFeCo perpendicular magnetic recording media

TiN thin film is prepared by DC reactive sputtering in Ar+N₂ atmosphere and its suitability as underlayer and overlayer for TbFeCo perpendicular recording media as well as its effect on the magnetic properties of the latter have been studied. Only 5 nm TiN overlayer and 20 nm under layer can successfully protect the TbFeCo film from oxidation. Initially the coercivity is increased sharply from about 2 to 6 kOe for an increase of underlayer thickness to 60 nm then the increasing rate of coercivity becomes very slow. The saturation magnetization remains almost constant with the underlayer thickness. The remanent squareness ratio remains constant at 1.0 with the underlayer thickness up to 60 nm then decreases.     

Current characteristics of barrier discharges in inert gases (Ar,Kr, Xe)

The current characteristics of barrier discharges in inert gases (Xe, Kr, and Ar) are compared. It is shown that the shape of the current curve (the number of peaks and their amplitudes) depends on the kind of gas (breakdown voltage) and the frequency of the sinusoidal supply voltage; as the frequency of the voltage decreases, the number of breakdowns tends to increase. It is found that, under the experimental conditions (P = 300 Torr, d = 4 mm), the amplitude of the discharge current in Xe is two to three times higher, its time is tenfold shorter, and the diameter of the discharge channel is five to ten times smaller compared to other inert gases. These differences can be explained by a considerable difference of the transfer coefficients in Xe from those in Ar and Kr.     

UV photoemission from physisorbed atoms and molecules: Electronic binding energies of valence levels in mono- and multilayers

Angle-resolved UV photoemission spectra were measured for Ar, Kr, Xe, CO, O₂ and N₂ adsorbed on a Ni(110) surface at 20 K. The different gases were adsorbed also on the Ni(110) surface which had been precovered by mono- and multilayers of the same gases. Upon physisorbing one of these species onto the bare and precovered Ni surface, binding energy shifts up to 3 eV were found. These shifts will be explained by work function changes of the substrate onto which the gas is physisorbed. It will be shown that for the investigated gases the binding energy referred to the vacuum level is an atomic or molecular property which is independent of the substrate, to a first approximation. By physisorption of a known gas the work function of any substrate can be evaluated by UPS. The density of valence states for bulk Ar, Kr and Xe will be discussed. There is evidence that the conduction band can be seen in the secondary electron background of the UP spectra.     

Effective suppression of internal stresses in Co-Cr films using a mixture of Ar and Kr as the sputtering gas

A lower sputtering gas pressure during the sputtering process tends to result in the deposition of denser Co-Cr films, but also increases compressive internal stresses when a mixture of Ar and Kr is used as the sputtering gas. The internal stresses have been reduced with an increase in the ratio of Kr in the gas mixture.     

具有条纹磁畴结构的NiFe薄膜的制备与磁各向异性研究

具有条纹磁畴结构的磁性薄膜表现出面内转动磁各向异性,对于解决高频电子器件的方向性问题起着至关重要的作用.本文采用射频磁控溅射的方法,研究了NiFe薄膜的厚度、溅射功率密度、溅射气压等制备工艺参数对条纹磁畴结构、面内静态磁各向异性、面内转动磁各向异性、垂直磁各向异性的影响规律.研究发现,在功率密度15.6 W/cm~2与溅射气压2 mTorr(1 Torr=1.33322×102Pa)下生长的NiFe薄膜,表现出条纹磁畴的临界厚度在250 nm到300 nm之间.厚度为300 nm的薄膜比250 nm薄膜的垂直磁各向异性场增大近一倍,从而磁矩偏离膜面形成条纹磁畴结构,并表现出面内转动磁各向异性.高溅射功率密度可以降低薄膜出现条纹磁畴的临界厚度.在相同功率密度15.6 W/cm~2下生长300 nm的NiFe薄膜,随着溅射气压由2 mTorr增大到9 mTorr,NiFe薄膜的垂直磁各向异性场逐渐由1247.8 Oe(1 Oe=79.5775 A/m)增大到3248.0 Oe,面内转动磁各向异性场由72.5 Oe增大到141.9 Oe,条纹磁畴周期从0.53μm单调减小到0.24μm.NiFe薄膜的断面结构表明柱状晶的形成是表现出条纹磁畴结构的本质原因,高功率密度下低溅射气压有利于柱状晶结构的形成,表现出规整的条纹磁畴结构,高溅射气压会导致柱状晶纤细化,面内转动磁各向异性与面外垂直磁各向异性增强,条纹磁畴结构变得混乱.     

Editorial

A high resolution electron spectroscopy technique is used to study the autoionization of noble gases excited by fast neutral noble gas atoms with 80–600 eV kinetic energy. The energy and notation of the excited states is determined by considering the proper quantum defects in the Rydberg series. The doubly excited states prevail over the singly excited ones. Like and unlike colliding pairs are studied and various excitation processes are suggested for the HeKr, ArKr and ArXe systems.     

Emission from impurity molecular centres in binary solutions of inert crystals

The structure of impurity excitations in solid binary solutions XeKr, XeAr, KrAr has been studied using the luminescence vacuum u.v. spectroscopy. Emission from biatomic heteronuclear molecules of inert elements was separated. The existence of two excited states of heteronuclear molecules of different atomic configurations is predicted. The pair potential of inert element interaction in the excited and ground states are analysed and force constants found. The peculiarities of the heteronuclear molecule formation as a function of concentration and temperature for solid binary solutions of inert gases have been discussed.     

Population processes in high-pressure inert-gas-mixture lasers

Working-level-population processes are analyzed on the basis of detailed investigations of the amplitude-time structure of the laser and spontaneous emission following a pulsed electric discharge in the mixtures He + R (R = Ar, Kr, Xe), Ar + Xe. Account is taken in the analysis of excitation by electrons (direct and stepwise) and of population as a result of relaxation processes (collisions of second kind with electrons; radiative cascades, recombination processes; collisions with the atoms of the working and buffer gases; excitation transfer from helium molecules). It is concluded that under optimum efficiency conditions inversion is produced in the lasers considered as a result of direct electron collision with the working atoms (Ar, Kr, Xe), which are in the ground state.Translated from Lazernye Sistemy, pp. 15–34, 1982.     

Influence of Ar,Kr, and Xe layers on the energies and lifetimes of image-potential states on Cu(100)

The influence of well-ordered adlayers of Ar, Kr, and Xe on the energetic and dynamical properties of image-potential states on Cu(100) has been investigated in a comprehensive study using time-resolved two-photon photoemission (2PPE). The effect of these insulating films varies systematically with the electron affinity EA of the condensed rare gases and with the film thickness. For the electron-repulsive Ar layers (EA=-0.25 eV), a strong lifetime increase of the n=1 state from 40 fs on clean Cu(100) to as much as 10 ps at a coverage of 5 monolayers is observed. For Kr and Xe layers (EA=+0.3 and +0.5 eV, respectively), decoupling from the metal is less efficient. These layers exhibit quantum-well-like resonances of the n=2 state as a function of layer thickness. The energies of the series of states depend characteristically on the affinity level and the dielectric constant of the films. A microscopic model is developed that includes the discrete atomic structure of the adsorbate layers. It is capable of describing the experimental results to a high degree of quantitative agreement. PACS 78.47.+p; 73.20.At; 77.55.+f     

An experimental investigation of the pressure and concentration dependence of muonic Coulomb capture and cascade in gases

Muonic Coulomb capture ratios and x-ray intensity patterns in four binary mixtures of the gases N₂, Ne, Ar, Kr, and Xe have been measured at three atomic ratios. An influence of the concentration has been established. The Lyman series intensity patterns of pure N₂, Ne, Ar, Kr, and Xe were measured at pressures between 0.4 and 51 bar and found to depend on the pressure. Possible explanations are discussed.     

Ti(Cr)缓冲层对用于垂直磁记录材料CoCrTa介质磁特性和微结构的影响

利用直流对靶磁控溅射技术在单晶Si衬底上制备了C/CoCrTa/X (X=Cr，Ti)介质材料.分别采用振动样品磁强计、X射线衍射仪、扫描探针显微镜对样品的磁性、微结构等进行了测试分析.研究发现，Ti缓冲层有利于样品中Co晶粒的易轴垂直于膜面生长.以Ti为缓冲层的样品，颗粒尺寸和表面粗糙度较小，而且磁畴明显，说明以Ti为缓冲层的薄膜样品更适宜做垂直磁记录. 关键词： CoCrTa 垂直磁记录 缓冲层 微结构     

Kr/Xe气体在塑料闪烁体表面的吸附与扩散行为研究

采用基于Compass力场的分子动力学(MD)方法,研究了惰性气体氙(Xe)和氪(Kr)在塑料闪烁体(聚乙烯基对甲苯)的平整和粗糙表面的吸附和扩散行为.由惰性气体吸附曲线的均方根位移(MSD),得到了Xe/Kr气体在聚乙烯基对甲苯表面的扩散系数.研究结果表明,Kr/Xe气体均被稳定地吸附在塑料闪烁体表面,其稳定性随着温度的升高而增加,Xe分子的吸附性强于Kr分子. Kr/Xe气体在聚乙烯基对甲苯表面具有较强的扩散性能,扩散深度随着温度与厚度的增加而增加,最大为22.865?,Kr分子扩散能力强于Xe分子.基底粗糙表面增加了两种惰性气体分子的吸附和扩散.     

Dependence of properties of hydrogenated microcrystalline and amorphous silicon films prepared by planar magnetron sputtering in inert gas

Microcrystalline and amorphous hydrogenated silicon films were preparaed by rf planar magnetron sputtering in the four kinds of inert gas, i.e., He, Ne, Ar, and Kr. The dependence of such properties as x-ray diffraction, ir spectra, absorption coefficient, hydrogen content, dark conductivity and photoconductivity on the kind of inert gas was investigated. Such deposition conditions as hydrogen partial pressure, sputtering pressure and rf power were also studied mainly in relation to the microcrystallization of the films. Microcrystalline films with noticeably high deposition rate could be obtained in the case of Kr and Ar, compared to the case of He and Ne. Hydrogen concentration was found to correlate to the photoconductivity and activation energy of dark conductivity except for the case of He. Photosensitivity was appreciably larger for amorphous film than for microcrystalline one. Especially in the case of Kr, it was considerably larger than in other cases.     

Totale Streuquerschnitte für den Stoß von H2, D2 und He an den Edelgasen Ne,Ar, Kr und Xe im thermischen Energiebereich

The velocity dependence of the total elastic cross section has been measured for the scattering of H₂, D₂, and He beams by Ne, Ar, Kr, and Xe gases. Velocity-selected beams were attenuated by gas in a scattering chamber. A universal detector, with a magnetic mass separator, was used in conjunction with lock-in techniques. The results are compared with quantum mechanical calculations using a Lennard-Jones-(12.6)-potential, and employing suitable averaging over experimental velocity distributions. Potential parameters are presented. These are in good agreement with those expected from other methods of measurement.     

多层膜［Co85Cr15/Pt］20的磁性、垂直磁记录特性和微结构的关系

采用磁控溅射法制备了性能优良的以Pt为缓冲层的［Co85₈₅Cr15_{15/Pt］2020 多层膜，研究了溅射气压对［Co8585Cr1515/Pt］2020多层膜微结构和磁性的 影响.研究结果表明，Ar溅射气压对［Co8585Cr1515/Pt］2020多层膜的微结构 、垂直磁各向异性和矫顽力有重要的影响 关键词： 溅射气压 多层膜 垂直磁各向异性 有效磁各向异性常数}     

Symmetry and Condensed Matter Physics – A Computational Approach,by M. El-Batanouny and F. Wooten

The behaviour of positrons below the inelastic collision threshold in rare gases can usually be completely accounted for in terms of the annihilation and elastic scattering cross sections for collisions between a positron and a single gas atom. Determining these cross sections has been the subject of many theoretical and experimental investigations. However the basic premise that the positron interacts with the gas atoms, one at a time, has been recently questioned by the yet unexplained results of some low-temperature experiments. This article discusses the annihilation and elastic scattering cross sections as they relate to the conventional picture of positrons in He, Ne, Ar, Kr and Xe gas; as well as the possibility of bound states for positrons in the gases at low temperatures.     

Spectral anomalies of the light-induced drift of rubidium atoms caused by the velocity dependence of transport collision frequencies

The spectral features of the light-induced drift (LID) velocity for rubidium atoms (⁸⁵Rb and ⁸⁷Rb) in an argon buffer medium and in binary buffer mixtures of noble gases (Ne + Ar, Ne + Kr, Ne + Xe, He + Ar, He + Kr, and He + Xe) have been investigated theoretically. A strong temperature dependence of the spectral shape of the LID signal for Rb atoms in an Ar atmosphere is predicted in the temperature range 450 K < T < 800 K. It is shown that the anomalous LID of Rb atoms in binary buffer mixtures of noble gases can be observed at almost any temperature (including the room one) depending on the fractions of neon or helium in these mixtures. The results obtained enable a highly accurate testing of the interatomic interaction potentials used to calculate the drift velocity for anomalous LID in LID experiments.     

Charge states of inert gas ions in lunar ilmenites

Fractionation of particles of solar corpuscular radiation significantly changes from flare to flare; therefore the average regularities derived from the contents of inert gases in lunar samples of different cosmicray exposure age are of particular importance. Simulation of the charge states of inert gas ions (Ne, Ar, Kr, and Xe) in lunar ilmenites suggests possibility of higher solar flare activity and higher hardness of the solar proton spectrum ～1 billion years ago.     

Excimers and excimer lasers

The development of excimers and excimer lasers are reviewed. The excimers of the noble gases (Xe ₂ ^* , Kr ₂ ^* , Ar ₂ ^* ) and of the noble gas halides (e.g. KrF, XeCl) which, respectively, radiate in the vacuum ultra-violet and ultra-violet regions of the spectrum are described in terms of their structure, spectroscopy and formation kinetics and the methods of pumping, operational characteristics and applications of the lasers are discussed.