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Today’s education places a strong emphasis on helping students become interculturally competent. Given its significance, the current study aims to evaluate the development of intercultural competence of undergraduate EFL students at the Ibn Khaldoun University of Tiaret. Because there are not many studies assessing or how to assess university EFL students’ intercultural competence in Algeria, it is necessary to research how much intercultural competence is incorporated into the current university English education program. Thus, the main question addressed is whether Algerian undergraduate EFL students have intercultural competence. To address this question, 36 third-year English major students at the Ibn Khaldoun University of Tiaret were randomly chosen to participate in the study. The measurement tool was a questionnaire with inquiries regarding the following three intercultural competence dimensions: attitudes, knowledge and skills. The findings of this study showed that although the participants’ intercultural attitudes and knowledge are high, they lack the intercultural skills that are essential for attentive intercultural speakers to interpret and use appropriate expressions associated with the cultural environment. As a result, this study strongly recommends that it is crucial to incorporate all the elements of intercultural competence in the current English curriculum at Algerian universities.

Countless research has spotlighted literature on foreign language’s linguistic, cultural, aesthetic, and critical thinking benefits as well as the models and strategies in connection with its effective teaching. Howbeit, based on our experience/observation, the provision of the ways/processes the literary competence should be assessed seems to be scarce. The need to assess the foreign language learners' literary competence as a learning outcome is vital. Therefore, as a contribution to this area of study, the present study aims at assessing EFL students’ literary competence. To do so, twenty-five randomly selected third-year English students at the University of Tiaret participated in the study, and O’Brien’s On the Rainy River was used as a data tool to measure their literary competence. Given the skills that literary competence embraces, the findings of this research revealed that the participants of the EFL students at the University of Tiaret lacked some basic skills that are essential for literary competence. In response to this, the paper suggests some recommendations for both teachers and students. Keywords: Assessment; Competence; EFL Students; Literature

The development of 21st century skills is now widely accepted as a vital competency for graduates to succeed in today's world-society and economy. Employers, students, and teachers' perceptions of the skill gaps have been the focus of some research looking at the relationship between 21st century abilities and student knowledge. There are not many researches on how teachers' awareness affects their students' acquisition of 21st century abilities. The question that arises from this study is if the EFL teachers in Algeria are aware of the 21st-century learning needs that are necessary to implement any educational program. The purpose of this study is therefore to examine the extent of Algerian EFL university professors' awareness of 21st-century abilities. The degree to which they are open to change can be ascertained by looking at their level of self-awareness. At the same time, it will shed light on the apparent disparity in educational attainment between English majors and their peers. There were 13 English language teachers from IbnKhaldoun University of Tiaret who volunteered to be part of the study in order to gather data, and both quantitative and qualitative data were collected using a questionnaire. There was a correlation between teachers' knowledge of 21st century skills and their readiness to use them in their classrooms, according to the findings. In order to fully integrate 21st century skills into the classroom, teachers must overcome certain significant pedagogical issues such as excessive class size, a lack of teacher training, and an absence of accompanying instruments and technology equipment. Researchers drew conclusions and recommendations based on their findings.

The interaction of organic C 60 molecules with germanene grown on Al(1 1 1) is investigated by experimental tools and calculations. By mean of scanning tunneling microscopy, we show that a single but disordered C 60 layer is formed upon deposition in the monolayer range. Density functional theory calculations indicate that van der Waals and electrostatic interactions are present between the C 60 layer and the germanene, without formation of covalent bond. Moreover, the C 60 molecules are adsorbed without major crystallographic and charge modifications at the interface between germanene and the Al(1 1 1) substrate. The predicted charge transfer from the Al(1 1 1) substrate to the C 60 molecules is very small, which means that the germanene layer acts as an electronic buffer between the highly electron attractor C 60 molecules and the large electron reservoir Al(1 1 1). This leaves the C 60 layer quite uncharged, and so preserves its electron attractor properties for further layers grown on it, in the design of new molecular sensors.

Currently, there is a tendency towards intercultural education as a major goal in foreign language teaching and learning. The importance of developing learners’ intercultural communicative competence has derived from the need to preparing foreign language learners, in general, and English learners in particular, for potential cross-cultural communication, in which they may encounter linguistic and cultural barriers. However, in our specific context- the English Department at the University of Tiaret and certainly in other academic contexts in Algeria, it is found that this goal is far from being reached. To bridge the gap, our main goal in this paper is to share some specific teaching practices, and showing concrete teaching models of intercultural education at the EFL department.

The electronic structure of germanene is investigated by high resolution photoemission and density functional theory calculations. The core level Al 2p and Ge 3d lines are measured on germanene grown on Al(111) by using synchrotron radiation. The Ge 3d line is shifted toward the low binding energies with respect to bulk Ge, and shows three components, reflecting the sites multiplicity of the germanene atomic structure. The calculations reveal a sizable charge localization at the germanene/Al(111) interface, a charge transfer from the Al surface atoms to the germanene, and the existence of three nonequivalent Ge sites with three different atomic Bader charges, in agreement with the photoemission measurements.

We investigate the interface between Au catalysts and a Ge(1 1 1) substrate. This system is achieved by dewetting an Au layer above the Au–Ge eutectic temperature. We show by high resolution transmission electron microscopy that a large amount of Ge can be moved over a surface of Ge(1 1 1) by using assistance of eutectic Au–Ge droplets. This localization is achieved thanks to the ability of nano Au–Ge droplets to incorporate a large amount of Ge and to release it by cooling down the sample at room temperature. This makes the localization process irreversible with respect to annealing at a very high temperature. The extra Ge supplied by precipitation is in epitaxy with the Ge(1 1 1) substrate. This reflects in macroscopic I(V) measurements.

Germanene, a 2D honeycomb structure similar to silicene, has been fabricated on Al(111). The 2D germanene layer covers uniformly the substrate with a large coherence over the Al(111) surface atomic plane. It is characterized by a (3 × 3) superstructure with respect to the substrate lattice, shown by low energy electron diffraction and scanning tunnelling microscopy. First-principles calculations indicate that the Ge atoms accommodate in a very regular atomic configuration with a buckled conformation.

The electrochemical and structural characterization of thermally grown oxides formed on nickel based alloys (type Inconel 600 and 690) at 350 °C and during different time was performed by impedance measurements and near field microscopy combining atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM). The impedance results allow discussing the influence of the oxidation time on the capacitance and the resistance of the oxide films. The results obtained by near field microscopy technique show that the film formed during low oxidation time has a small grain size and also a small surface roughness. The values of grain sizes determined in both cases along x- and y-axis are practically the same indicating a spherical shape of oxide grains and are slightly different between oxides formed on type inconel 600 and 690.

The molecular-beam-epitaxy growth of Fe–Ge/Ge/Fe–Ge trilayers on Ge(111) wafers has been investigated as a function of three parameters: the Ge spacer coverage, the substrate temperature (TD) and the dynamic atomic hydrogen (H) exposure during the Ge spacer deposition. Morphology and crystal structure have been characterized in situ by means of scanning tunneling microscopy, low energy electron diffraction, X-ray photoelectron diffraction and ex situ with high-resolution transmission microscopy. Whatever the H flux, epitaxial growth of Ge spacer requires deposition temperature above ~ 220 °C. At the earliest stages of Ge deposition, the surface periodicity of the bottom Fe1.9Ge epilayer changes from p(2 × 2) to 3 × 3 R 30 ° for deposition temperature above ~ 220 °C, whatever the H dosing. It results from severe intermixing that modifies the stoichiometry of the whole Fe–Ge layer. However, this layer preserves its hexagonal B82 crystal structure and no additional Fe–Ge compounds formed at the interface. We found also that the H flux drastically modifies the Ge spacer growth mode for deposition temperature above ~ 220 °C. In particular, the Ge morphology evolves from 3D islands without H supply to flat and continuous film for H partial pressure above 10–3 Pa. Finally, the top Fe–Ge electrode crystallizes in the same structure as the bottom electrode, and the planar relations of the trilayer are: (111)Ge-wafer||(0001)bottom–Fe1.9Ge||(111)Ge-spacer||(0001)top–Fe1.9Ge and [− 110]Ge-wafer||[11–20]bottom–Fe1.9Ge||[1–21]Ge-spacer||[11–20]top–Fe1.9Ge. These fully epitaxial Fe–Ge/germanium hybrid heterostructures with single crystal Ge layer of diamond structure appear therefore as promising candidates for semiconductor spintronics.

Thermally oxidized AISI304 and AISI316 stainless steels are studied by Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy (SKPFM) and Magneto-Optical Kerr effect as a function of their growth temperature. The surface roughness is a competition between the roughness of the bare substrate and the roughness resulting from the oxide layer growth. Cr oxide is present at some places on the surface at low growth temperature as shown by SKPFM. The observed decrease of surface potential with the oxide layer thickness indicates an effective protection against corrosion. Magnetic measurements demonstrate that the outer layer contains a magnetite phase (in-plane magnetization).

The influence of Si capping layers on the magnetic properties of thin Fe films grown on Si(1 1 1) has been studied by means of shape anisotropy calculations. Fe surface morphology simulations are realized using experimental STM data. Surface modifications induced by the interaction between the Si overlayer and the Fe surface are performed in agreement with the model proposed in a previous work by Stephan et al. [J. Magn. Mater. 293 (2005) 746]. Calculations of the uniaxial anisotropy energy constant K u are then performed on the modified Fe surface morphology for different Si deposition geometries as proposed in the model. The relevant data deduced by this method such as anisotropy constants and their related easy axis direction, are directly compared to the experimental ones obtained by ex situ magneto-optical Kerr effect (MOKE) measurements at room temperature using the transverse bias initial inverse susceptibility and torque (TBIIST) method. We show that a very good agreement between those results leads to a confirmation of the proposed model.

This article presents the results obtained from the analysis of the I–V electrical characteristics of photovoltaic arrays that were tested in a region of the Sahara. Experiments were carried out at Adrar in the southern part of Algeria. The study includes the determination of the most representative parameters of the arrays by using numerical methods for the one exponential model. After having determined these parameters, they were numerically used in order to carry out the plotting of the theoretical I–V characteristics of modules for the considered environmental variables such as ambient temperature and solar irradiance. Other model (Rauschenbach's model) has also been considered in this article to make a comparison with the previous one. The study has been completed by carrying out the translation of the experimental characteristics for the standard conditions. This translation allowed the comparison to be made between the performances of tested modules. In the last part of the paper, some elements related to the degradation of arrays performances have been presented.

The magnetic and structural properties of epitaxial Fe films grown on Si(111) are investigated by polarized neutron re. ectometry (PNR) at room temperature. The influence of different types of interfaces, Fe/Si, Fe/FeSi2 and Au/Fe on the magnetic properties of Fe films deposited by molecular beam epitaxy onto Si(111) are characterized. We observe a drastic reduction of the magnetic moment in the entire Fe film deposited directly on the silicon substrate essentially due to strong Si interdiffusion throughout the whole Fe layer thickness. The use of a silicide FeSi2 template layer stops the interdiffusion and the value of the magnetic moment of the deposited Fe layer is close to its bulk value. We also evidence the asymmetric nature of the interfaces, Si/Fe and Fe/Si interfaces are magnetically very different. Finally, we show that the use of Au leads to an enhancement of the magnetization at the interface. (C) 2008 Elsevier B.V. All rights reserved.

We report on the investigation of structural and magnetic properties of the ternary Heusler alloy Co 2 MnSi grown on Si(0 0 1) by molecular-beam epitaxy. Low-energy electron diffraction (LEED), inelastic medium-energy electron diffraction (IMEED) and X-ray photoelectron diffraction (XPD) measurements clearly show the growth of crystalline Co 2 MnSi . The best crystallographic and magnetic quality of the Co 2 MnSi films have been achieved after codeposition of the three Co, Mn and Si elements on the Si(0 0 1) substrate held at 587 K. Quantitative determinations of magnetic anisotropies were performed using transverse bias initial inverse susceptibility and torque measurements (TBIIST). Co 2 MnSi reveals to have an in-plane fourfold magnetocrystalline anisotropy with easy axis along 〈 0 1 0 〉 directions for evaporation fluxes perpendicular to the substrate surface. On the other hand, grazing-incidence fluxes invariably generate a dominant uniaxial in-plane magnetic anisotropy contribution with easy axis perpendicular to the incidence plane.

The strain state of Fe films grown on Si(1 1 1) has been investigated by X-ray diffraction (XRD) in the thickness range between 11 and 304 monolayers. Fe grows tetragonally distorted with the orientation relationship Fe(1 1 1) 〈 1 2 ¯ 1 〉 // Si(1 1 1) 〈 1 ¯ 2 1 ¯ 〉 . At low coverage, the films grow pseudomorphic. Above 15 monolayers the films are characterized by the coexistence of a pseudomorphic phase with another one which relaxes with the Fe thickness. This relaxation proceeds rapidly in the earlier stages then slowly with the film thickness. The XRD characterization allows one to obtain quantitative information on the in-plane and out-of-plane strains.

We present a sensitive and precise determination of an arbitrary thin film magnetic anisotropy energy E a (or E a / M S if the saturation magnetization M S is not known) versus in-plane polar angle θ by means of initial inverse susceptibility and torque measurements under constant transverse bias field H B . In this method coined TBIISTtwo magnetic fields H L and H B are applied in the plane of the film along directions defined by θ and θ - ( π / 2 ) , respectively, and m L the magnetization component in units of M S is measured versus H L around m L = 0 . This readily provides two quantities χ - 1 = ( ∂ H L / ∂ m L ) ( m L = 0 ) the initial inverse susceptibility and Δ H = H L ( m L = 0 ) the field offset or torque at m L = 0 , shown to be respectively related to the second ( 1 / M S ) ( ∂ 2 E a / ∂ θ 2 ) ( θ - ( π / 2 ) ) and first ( 1 / M S ) ( ∂ E a / ∂ θ ) ( θ - π / 2 ) derivatives of E a . This, in turn, yields two determinations of E a ( θ ) from χ - 1 ( θ ) and Δ H ( θ ) , respectively. Fourier analysis then easily resolves various contributions of different symmetries to the magnetic anisotropy. The magnetization m L ( H L ) is measured with a conventional magneto-optical Kerr experiment in longitudinal geometry with respect to H L and higher-order (nonlinear in m L ) contributions as well as polar or other contributions to the Kerr signal are carefully determined and corrected in order to obtain the desirable accuracy or even simply meaningful results. Typical acquisition times including all corrections are about a few minutes per angle θ . The power of the method is demonstrated on typical examples of epitaxial Fe layers on Si(0 0 1) and Si(1 1 1) substrates. For instance, it is shown that extremely small contributions up to the 12th order in-spin to the cubic magnetocrystalline anisotropy of iron are readily detected.

We demonstrate that an in-plane uniaxial magnetic anisotropy can be induced in Fe films grown on Si(1 1 1) by means of an appropriate Si capping layer. It is shown that grazing-incidence Si deposition reduces the three-fold symmetry of the body-centered-cubic (BCC) Fe(1 1 1) surface to two-fold, thus generating a surface-type uniaxial in-plane magnetic anisotropy contribution. The relevant magnetic easy axis direction depends in a critical way on the azimuth of the Si evaporation flux with respect to the Fe crystal surface directions. A simple qualitative model based on the change of the Fe surface by inhomogeneous chemical reaction with Si is proposed to interpret the magnetic anisotropy evolution.

The correlation between growth and magnetic anisotropy of thin Fe films deposited on ultra thin iron silicide template grown on Si(111) is investigated by means of scanning tunnelling microscopy and magneto optical Kerr effect experiments. The morphology of the film strongly depends on the Fe beam orientation relative to the sample normal. Whereas the Fe clusters are randomly distributed at normal incidence, oblique evaporation leads to the formation of elongated Fe islands perpendicular to the Fe beam. These distinct growth modes lead to drastically different magnetic anisotropies. An in-plane six-fold anisotropy magnetic easy axis has been evidenced for films deposited at normal incidence. The films evaporated at oblique incidence show an uniaxial in-plane magnetic easy axis parallel to the Fe stripes. This uniaxial anisotropy originates from long-ranged dipolar interactions. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Combined transverse biased initial inverse susceptibility and torque measurements were performed on thin Fe(1 1 1) films epitaxially grown on Si(1 1 1), using a conventional magneto-optical Kerr effect magnetometer. This new method, called TBIIST, is a well suitable and sensitive technique for the study of magnetic anisotropies and in particular provides an accurate value of the anisotropy field strength in the sample and a precise determination of the anisotropy axes. For this purpose a 160 monolayer Fe film grown on Si(1 1 1) at normal incidence was investigated. A very small sixth-order contribution to the cubic anisotropy is readily detected, as expected for a Fe(1 1 1) film, corresponding to anisotropy fields as low as a few tenths of an Oersted.

Structural information on ultrathin films of Fe x Co 1− x alloys grown epitaxially by coevaporation on Si(0 0 1) at room temperature is obtained by X-ray photoelectron diffraction, low-energy electron diffraction, inelastic medium-energy electron diffraction and transmission electron microscopy. The body-centered-cubic structure is found to be stabilized for alloy thin films up to very high concentration of Co beyond the thermodynamically stable bcc range (0.25⩽ x ⩽1). For alloy films with thickness up to 10 monolayers, the bcc structure with (0 0 1)[1 0 0]Fe x Co 1− x //(0 0 1)[1 0 0]Si is actually observed over the entire range of alloy concentrations that includes elemental bcc Co. All films are ferromagnetic with in-plane magnetization. They show clear in-plane fourfold magnetic anisotropy for all alloy concentrations and the relevant cubic anisotropy constant shows a strong composition and thickness dependence.

Epitaxially grown iron thin films (thickness: 8 A < d < 120 A) on Si(0 0 1) with body centred cubic structure have been structurally and magnetically studied at room temperature. All lilms are characterized by ferromagnetic properties as soon as the thickness reaches 4 ML. In-plane uniaxial and cubic magnetic anisotropy constants are measured on samples obtained by modifying the incidence angle of evaporating iron flux. The magnetization reversal mechanisms are analyzed by combining longitudinal magneto-optical Kerr effect of both parallel and transverse magnetization components. These mechanisms are strongly influenced by the nature of the magnetic anisotropies.

The magnetic properties of epitaxial iron films up to 80 monolayers (ML) thickness grown on Si(0 0 1) by using a template technique were investigated by means of superconducting quantum interference device and magneto-optic Kerr effect techniques. The thinnest films investigated (∼3 ML) exhibit a composition close to Fe3Si with a Curie temperature below room temperature (RT) and strong out-of-plane remanent magnetization that reflects the presence of a dominant second order surface anisotropy term. Thicker films (⩾4 ML) are ferromagnetic at RT with remanent magnetization in film-plane and a composition closer to pure Fe with typically 8–10% silicon content. When deposited at normal incidence such films show simple in-plane fourfold anisotropy without uniaxial contribution. The relevant fourth-order effective anisotropy constant K4eff was measured versus film thickness and found to change its sign near 18 ML. The origin of this remarkable behavior is investigated by means of a Neel model and mainly traced back to fourth-order surface anisotropy and magneto-elastic effects related to the large biaxial in-plane compressive strain up to 3.5% in the thinnest (⩽25 ML) films.

We demonstrate the possibility of growing good-quality epitaxial Fe films on a Si(001) substrate, opening up new prospects to prepare ferromagnetic superlattices on this substrate. A template technique prevents the formation of disordered interfacial iron silicides. Transmission electron microscopy reveals that the Fe layers are fairly uniform in thickness with abrupt interfaces and in majority epitaxial relationship Fe(001)[100]//Si(001)[100]. Both the diffraction data and the observation of Moire fringes indicate that the Fe lattice is almost relaxed towards its bulk bcc phase in thick layers [≥40 monolayers (ML)] but is still strained by the substrate in the thinnest films. Magneto-optical Kerr effect measurements show that the films evaporated at normal incidence with a thickness above 4 ML are ferromagnetic at room temperature and exhibit in-plane biaxial anisotropy.

Binary Fe(Si 1− x Fe x ) iron and ternary Fe 3− y Co y Si iron cobalt silicide thin films (thickness : 200 A) with local CsCl structure epitaxially grown at room temperature on Si(1 1 1) have been studied through X-ray magnetic circular dichroism (XMCD) and magneto-optic Kerr effect (MOKE) vector magnetometry. The binary Fe(Si 1− x Fe x ) films have ferromagnetic properties at room temperature in the range 0.09⩽ x 3− y Co y Si films are ferromagnetic as well in the whole range 0 y 3 Si) favored by the absence of orientation dependence of the fourth-order cubic term of the magnetocrystalline anisotropy energy in (1 1 1) crystallographic plane. The easy axis corresponds invariably to the direction normal to the incidence plane of the atomic flux during evaporation. The substitution of iron by silicon in Fe(Si 1− x Fe x ) films increases the coercive field but does not strongly affect the uniaxial anisotropy constant. In Fe 3− y Co y Si alloys, a similar trend is observed and the increase of coercive force may be related to defects generated by alloying. The change of the magnetic moments of Fe and Co versus y , as obtained by XMCD, can be understood in terms of simple models.

Iron silicide thin films (200 A Fe(Si 1− x Fe x ) with 0⩽ x ⩽1 and local cubic CsCl structure) have been grown by coevaporation at room temperature (RT) on Si(1 1 1). X-ray magnetic circular dichroism (XMCD) and magneto-optic Kerr effect (MOKE) measurements indicate that the films are ferromagnetic at RT for x ranging from 1 (pure Fe) to 0.15 (Fe 1.35 Si). The magnetization is parallel to the film surface, and the magnetic anisotropy is uniaxial, with the easy axis lying along a [1 0 1] Si crystallographic direction and the hard axis along a [1 2 1] Si direction of the substrate. MOKE measurements show that the magnitude of the saturation field increases with increasing Si concentration, while XMCD data indicate that the average local magnetic moment carried by the Fe atoms decreases with decreasing Fe concentration. Models which involve the diminution of the number of Fe nearest neighbors are proposed for the description of the behavior of the Fe moments.

We investigated the coupling of specific ferroelectric-superconducting composites with variable volume fraction, particularly because they have presented a superconducting transition at 85 K. The intra- and intergranular coupling of these composites has been considered from the resistivity and susceptibility measurements. Our results show that the transport properties of this kind of composite are governed by different mechanisms, depending on the volume fraction of the ferroelectric material, . Up to intragranular coupling exists between the YBCO superconducting grains, but when the electrical transport is greatly related to intergranular coupling. In this case, two distinct and superconducting phases are evidenced by the susceptibility measurements; they maintain the superconducting character of the composites. Moreover, at the superconducting percolation threshold, the electrical response exhibits some hysteresis giving evidence that internal polarization is important and can play a role in the composite properties.

We present experimental results obtained for R Ba 2 Cu 3 O 7 − x ( R = Y,Er) expitaxial thin films obtained through pulsed laser deposition (PLD) and grown on yttria stabilized zirconia (YSZ) and SrTiO 3 (STO) substrates. The films have been deposited by using low deposition rates ( f = 4 Hz) and with control of the film surface temperature rather than that of the sample holder leading to a high quality of the epitaxy.

RE 1 Ba 2 Cu 3 O 7-δ (RE = Er or Y) superconducting films were fabricated by reactive laser deposition, in situ, on YSZ(100), SrTiO 3 (100) and Si(001), under various conditions. A complete XRD investigation showed that the films grown with high substrate temperatures (T s > 740°C) combined with low fluences (1.5 J / cm 2 < 2 J / cm 2 ) and laser repetition rate (4 Hz) have the best structural characteristics, very good electrical and magnetic properties.

Complex a.c. susceptibility measurements in a broad field range () have been made on Bi - Pb - Sr - Ca - Cu - O (Bi-2223 phase) bulk samples obtained by combined magnetic melt texturing and hot pressing. Highly anisotropic properties are observed. Improved intergranular coupling is obtained in the direction perpendicular to the applied stress and the magnetic field direction. An intragranular peak is also observed for the same direction. This is the first time that an intragranular loss peak has been clearly seen in a bismuth-based compound, which indicates that the intragranular contribution is strongly increased.

Initial AC susceptibility measurements on REBa2Cu3O7−δ (RE = Y, Er), Bi2Sr2CaCu2O8+δ and HgBa2Ca2Cu3O8+δ polycrystals are used in order to obtain the irreversibility lines (IL) in the (hac, T) plane. The deviation of IL from linearity below a critical field value h c ∗ is discussed and related to the dimensionality of the compound. The effects of the fabrication techniques are also discussed.

Low field a.c. susceptibilities of HgBa 2 Ca 2 Cu 3 O 8+δ (Hg-1223) and Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212) have been studied. The loss peak of χ″, relevant to intergranular pinning, shifts to higher temperatures for increasing frequencies. The results can be fitted with an Arrhenius law, leading to activation energies E a ≈ 1eV, but the hopping frequencies 0 are not realistic. More realistic values can be obtained by introducing a Fulcher law or a power law which is also characteristic of strongly interacting systems.

The complex AC susceptibility of HgBa2Ca2Cu3O8+δ(Hg-1223) has been studied for DC magnetic fields 0 Oe≤HDC≤50 Oe and AC magnetic fields 0.1 Oe≤hAC≤70 Oe allowing the determination to be made of the irreversibility line both in the (HDC, T) plane and in the (hAC, T) plane. The critical dynamic field h∗c has furthermore been obtained in the low AC field limit. All these results are consistent with a strong increase of the intergranular pinning strength which is one order of magnitude higher than in similar as-sintered 123 compounds, suggesting possibilities for the critical currents.

International audience; We investigate the chemical and morphological structure of the Au nanodots on Ge(111) which serve as catalysts for the formation of epitaxial Ge nanowires. The spatial localization of Au is investigated by X-ray spectromicroscopy and transmission electron microscopy. We show that dewetting of an Au film on Ge(111) gives rise to a thin Au-Ge wetting layer and Au-Ge dots. These dots are crystallized but not with a single crystallographic orientation. Thanks to the spatially resolved X-ray and transmission electron microscopy measurements, a chemical characterization of both binary Au-Ge catalysts and wetting layer is obtained at the nanoscale. We show that Ge vertical growth is achieved even without external Ge supply.

Low AC field magnetic phase diagrams in the (hAC,T) plane have been deduced from AC susceptibility measurements for YBa2Cu3O7- delta sintered polycrystals, magnetically melt-textured polycrystals and single crystals. It is shown that dissipative regimes appear in all cases above a critical line located well below the irreversibility line, and the strongest shifts of the critical line against the irreversibility line are observed in magnetically melt-textured polycrystals. The relative positions of the irreversibility lines show that the increase of jc in magnetically melt-textured polycrystals is relevant to the creation of pinning sites with high activation energies.

Characterization of a superconducting transition is commonly achieved by a.c. susceptibility measurements. The technique involved is rather simple, but interpretation of experimental results in inhomogeneous compounds such as superconducting ceramics is difficult because of the great sensitivity to numerous experimental parameters which also govern sample fabrication techniques (geometry, stoichiometry and thermal treatment) and measuring conditions (frequency, magnitude and orientation of the a.c. and/or d.c. magnetic fields). We present an analysis of both the real part x′ and the imaginary part x″ of the complex susceptibility x = x′ + i x″ in the low field limit which allows an effective comparison between various superconducting ceramics. A review of experimental results includes comparison of flux pinning strength (given by the critical dynamic field h c ∗ ) and phase diagram in the ( h a.c. , T ) plane. The critical line obtained in such a way differs markedly from the so-called “irreversibility line”.

The growth of thin Fe films deposited at oblique incidence on an iron silicide template onto Si(1 1 1) single crystal has been investigated as a function of Fe thickness (0 t Fe ⩽ 180 monolayers (MLs)) and incidence angle (0 ⩽ θ ⩽ 80°). The growth mode is determined in situ by means of scanning tunnelling microscopy (STM) and low energy electron diffraction (LEED). Stripes oriented perpendicularly to the incident atomic flux are formed for θ ⩾ 30°. Self-correlation functions are used to extract characteristic lengths from STM images. The correlation lengths in the direction of the incident flux ( ξ x ) and perpendicular to the atomic flux ( ξ y ) grow with different powers versus time ( ξ x ∝ t σ and ξ y ∝ t ρ , with σ = 0.34 ± 0.03 and ρ = 0.67 ± 0.03) following the exact solution of the (1 + 1) dimensional Kardar–Parisi–Zhang (KPZ) equation. The root mean square roughness follows also a scaling law for t Fe β = 0.73 ± 0.02. Shadowing and steering effects are discussed on the basis of our STM data.

We discuss the problem of characterizing a superconducting transition and the question of comparing samples originating from different fabrication processes and/or obtained under various shapes or morphologies (bulk, wires, thin films, single crystals, …). We present two different methods for the analyses of the AC susceptibility (for both the real and the imaginary part) in the low field limit. Strength of flux pinning and intergrain/intragrain contributions are discussed. Both analyses are applied to different inhomogeneous superconductors like high-Tc compounds (YBCO, LCO, LSCO, LBCO, B(P)SCCO, NCCO), Chevrel phases, etc. The dynamic critical field given by such an analysis allows an estimation of the quality and/or homogeneity of the superconducting sample and is a measure of the first intergrain (or Josephson) critical field.

We discuss the problem of characterizing a superconducting transition and the question of comparing samples originating from different fabrication processes and/or obtained under various shapes or morphologies (bulk, wires, thin films, single crystals, …). We present different methods for the analysis of the very low field a.c. susceptibility (for both the real and the imaginary part). The dynamic critical field obtained from our analysis (which can be applied to different inhomogeneous superconductors like high T c compounds, Chevrel phases, etc.…) is a measure of the quality and/or homogeneity of the superconducting sample.

International audience; We report on the epitaxial growth of ultrathin ferromagnetic Fe1.7Ge layers on Ge111 wafer. These single crystal intermetallic layers adopt the InNi2 B82 crystallographic structure. They are ferromagnetic with a Curie temperature well above room temperature. The interface between the ferromagnet layer and the Ge wafer is of high perfection. Interestingly, the annealing of the sample up to 300 °C alters neither the crystallographic structure, nor the interface quality, nor the magnetic properties but leads to a nearly perfect smoothening of the germanide layer surface. This high thermal robustness should open the way for the growth of fully epitaxial iron germanide/Ge hybrid structures.

The controversial shapes of the transition in HTSC (e.g. width and ac field amplitude dependences) are resolved by introducing the dynamic critical field deduced from our susceptibility measurements. The dynamic critical field criterion (which is also a quality factor) is studied for various compounds (YBaCuO, BiSrCaCuO) and morphologies (bulk- and single crystals, thin films, wires) by studying the ac field dependences of both the real and imaginary parts of the initial susceptibility over nearly five orders of magnitude and down to very low ac fields (0.02 mOe h ac

A comparative study of the low field susceptibility of 123 high temperature superconducting compounds and Bi compounds is presented. Results are discussed using the dynamic critical field model of Mehdaoui et al. (1989,1990). The low critical dynamic fields and the corresponding low pinning energies obtained in the case of Bi compounds (when compared with 123 compounds) are consistent with other data about activation energy and explain the dependence of electrical resistivity upon measuring currents. The high temperature phase (Tc=110 K) also has much higher pinning than the low temperature phase (Tc=80 K) in the Bi compounds.

When discussing critical properties of inhomogeneous high temperature superconducting compounds it is preferable to compare experimental data collected from the greatest possible number of published results. However, such comparison is made difficult because of the wide variety of elaborate techniques, thermal treatments, characterization methods and sample morphologies involved in the experimental work reported in the literature. Here a phenomenological model, based on Clem's formulation and utilizing very low a.c. susceptibility measurements, is presented which demonstrates the existence of a critical field, h c ∗ , corresponding to the appearance of flux pinning. The analysis allows the classification of a large variety of high temperature superconductors including bulk samples, thin films and single crystals; the strength of the critical dynamic field (varying over three orders of magnitude: 50 mOe c ∗ Oe ) is a measure of the quality (and also homogeneity) of the sample. The analysis applies to YBaCuO compounds as well as to LaBaCuO and BiSrCaCuO compounds or Chevrel phases. The best quality appears to be for YBaCuO single crystals, while sintered BiSrCaCuO exhibits peculiar behaviour with very low h c ∗ or no h c ∗ at all.

Ferromagnetic films evaporated at oblique incidence show invariably an uniaxial in-plane magnetic anisotropy component with easy axis perpendicular to the incidence plane. Scanning Tunneling Microscopy (STM) images reveal that oblique deposition results in rough films with highly anisotropic correlation functions of the surface profile. We show that simple shape anisotropy calculations using high-quality STM roughness data as input reproduce the measured anisotropies remarkably well and unambiguously relate them to the long-ranged dipolar interactions.

Good quality body-centered cubic iron layers can be grown on Si(001) at room temperature using thin ${\mathrm{FeSi}}_{2}$ or ${\mathrm{CoSi}}_{2}$ silicide buffer layers. The in-plane and out-of-plane strains are measured by x-ray diffraction (XRD). Due to the difference in Fe and Si parameters of +5.6%, the thin Fe layers undergo a strong tetragonal distortion. For the samples deposited on ${\mathrm{FeSi}}_{2},$ the measured biaxial in-plane compressive strain ranges from values as large as -3.8% in the thinnest films (25 ML) to -1% in the thicker layers (g40 ML). In the samples deposited on ${\mathrm{CoSi}}_{2},$ a part of the iron layer clearly observable up to 40 ML, apparently grows in pseudomorphy with the silicon, whereas another dominant part above 15 ML partly relaxes and behaves as on ${\mathrm{FeSi}}_{2}$ templates but with systematically larger strains. The evolution of the in-plane cubic effective magnetic anisotropy constant versus Fe film thickness observed in previous work, can be explained by means of fourth-order (in spin) magnetoelastic coupling in the iron lattice with the strain components determined by XRD. Finally, the observed ratio between the perpendicular and in-plane strain components differs substantially from linear elasticity theory predictions and indicates the importance of anharmonic effects and/or defects in the description of the elastic properties of such films.

ac initial susceptibility of sintered, field textured, zone melted polycrystals and single crystals has been studied in the low field limit. Critical dynamic fields (h c ∗ ) and relative position of irreversibility line (I.L) and critical line (C.L) are consistent with the creation of strong pinning sites. High anisotropy is observed in the case of field textured samples.

The irreversibility line (I.L.) is often deduced from initial susceptibility measurements and taken at temperature TM corresponding to the maximum of the imaginary part χ″ of the susceptibility. It is expected that such a line plays a part analogous to that of the Tg (spin freezing temperature) in spin glasses, i.e. leads to a phase diagram in the H, T plane. But TM corresponds to the strongest dissipations and low field initial susceptibility measurements have shown that dissipations already occur well below the χ″ susceptibility maximum, and even in zero d.c. fields. We discuss an alternative way to define a critical line separating reversible and irreversible regimes; such a line is obtained (in a 3D extended phase diagram) by analyzing the χ′ real part of the initial susceptibility in the low a.c. field limit. It also represents the limit between dissipative and non dissipative regimes.

The authors present a detailed investigation of the AC field amplitude dependence of the initial complex susceptibility of YBaCuO compounds with various morphologies (bulk, thin film, single crystal) and BiSrCaCuO bulk compounds. They discuss the results together with published data in the critical dynamic field (hc*) model. hc* is a measure of the magnetic field above which vortices are unpinned giving rise to energy losses. The highest hc* are observed in YBaCuO single crystals. A comparison between YBaCuO and BiSrCaCuO polycrystals shows a better quality for the former. The magnetic transitions in YBaCuO compounds also show high sensitivity to grain size.