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Abstract: Nanometer scale layered systems are well suited to investigate atomic transport processes induced by high-energy electronic excitations in materials, through the characterization of the interface transformation. In this study, we used the atom probe technique to determine the distribution of the different elements in a (amorphous- multilayer before and after irradiation with Pb ions in the electronic stopping power regime. Atom probe tomography is based on reconstruction of a small volume of a sharp tip evaporated by field effect. It has unique capabilities to characterize internal interfaces and layer chemistry with sub-nanometer scale resolution in three dimensions. Depth composition profiles and 3D element mapping have been determined, evidencing for asymmetric interfaces in the as-deposited sample, and very efficient Fe–Co intermixing after irradiation at the fluence ion . Estimation of effective atomic diffusion coefficients after irradiation suggests that mixing results from interdiffusion in a molten track across the interface in agreement with the thermal spike model. [Copyright &y& Elsevier]

Abstract: The modification of the magnetic and magnetostrictive properties of TbFe2/Co exchange-coupled multilayers irradiated with 700MeV Pb ions was investigated as a function of ion fluence. After irradiation, the magnetostrictive properties of the sample are first strongly improved up to a fluence of 1×1012 ionscm−2 where the magnetoelastic susceptibility is six times higher than for the as-deposited sample. This effect is ascribed to stress relaxation and Fe–Co intermixing at the interfaces. For higher fluences, the magnetostrictive properties do not vary further, indicating a stationary state of mixing. [Copyright &y& Elsevier]

Abstract: Magnetic measurements are reported on iron and chromium powder mixtures, obtained by mechanical alloying (MA) over the whole concentration range. Magnetization measurements under high and low magnetic field were performed in order to characterize the influence of the nanostructure on magnetic properties. Magnetic results for MA FeCr powders can be interpreted, in agreement with previous Mössbauer results at 300K, taking into account two contributions: a contribution associated with the FeCr nanograin core and a contribution associated with the weakly magnetic disordered intergranular zone. In common with bulk FeCr alloys, MA FeCr powders seem to preserve a spin-glass-like (SGL) behavior, but over a greater range of composition depending on how they are made; the higher the grain boundary fraction, the wider the SGL domain and the lower the freezing temperature. [Copyright &y& Elsevier]

Abstract: Iron and chromium powder mixtures were elaborated by mechanical alloying (MA) from 0 to 30h of milling times and over the whole concentration range. Mössbauer spectrometry was performed in order to characterize the influence of the nanostructure on magnetic properties, especially of the intergranular zone. Mössbauer results at 300K show that the properties of MA FeCr powders alloying over the whole concentration range can be interpreted taking into account two contributions: a contribution associated with the FeCr nanograin core, which is very close to the FeCr bulk alloy with the same composition and contribution associated with the weakly magnetic disordered intergranular zone, created by gases dissolved during milling. [Copyright &y& Elsevier]

Mechanical alloying (MA) of iron and chromium powder mixtures was performed from 0 to 190 h. SEM, transmission electron microscopy with energy-dispersive X-ray analyses and Mo¨ssbauer spectrometry were used to study the mixing at micrometric and nanometric scale. At the stationary mixing state (≈20 h of milling), MA of Fe60Cr40 powder mixtures gives particles of several micrometers consisting of magnetic nanograin cores characteristic of crystalline Fe60Cr40 alloy surrounded by a disordered paramagnetic grain surface (at 300 K), which increases during milling. At 85 h, the nanograins are totally disordered. For a longer time of milling, a de-mixing occurs by partial recrystallization of this disordered structure. [Copyright &y& Elsevier]

Sr1−xLaxFe12−yCoyO19 powders with y/x=0.75 and x=0.1, 0.2, 0.3, 0.4 were prepared according to a ceramic process. X-ray diffraction analysis shows that all the powders are of single, hexagonal M-type, phase. The Mo¨ssbauer investigation confirms that Co2+ substitutes for Fe3+ in both 4f2 (mainly) and 2a sites. The most important hyperfine parameters changes concern the 12k, 4f2 and 2b sites and are related to both Co2+/Fe3+ and La3+/Sr2+ substitution effects. [Copyright &y& Elsevier]

Sputtered (TbCo2.5 25 nm/Fe 20 nm) multilayers have been analyzed by laser-assisted tomographic atom probe. It allowed us to perform three-dimensional reconstructions of the layers and to determine their composition at the atomic scale. From the concentration profiles inside the multilayer, we show that the diffused interfaces are not symmetric and that a stronger Fe-Co mixing is present at the top of the crystalline iron layers as compared to the top of amorphous TbCo layers. [ABSTRACT FROM AUTHOR]

Discusses the reproducible random composites of ferrimagnetic crystals and paramagnetic amorphous latent tracks generated by high energy heavy-ion irradiation of magnetic insulators. Third domain induced by high-energy heavy-ion irradiation of the garnet ceramics Y[sub 3]Fe[sub 5]O[sub 12]; Analysis of the Mossbauer spectra.

Investigates the interfacial reactions and evolution of the magnetic anisotropy in Tb/Fe multilayers irradiated by swift heavy ions. Formation of compositionally amorphous FeTb alloy regions at the interfaces in the vicinity of the ion path; Use of a phenomenological model to explain the evolution of the magnetic anisotropy.

Abstract: Longitudinal extraordinary Hall Effect (LEHE) of magnetic Tb(Fe0.55Co0.45)1.5 (known as Terfecohan) thin films with perpendicular magnetic anisotropy has been investigated as a function of both the intensity of applied magnetic fields and the angle α between the applied field and film normal directions. The Hall voltage loops exhibit a parallelogram shape, which is almost similar to those of the perpendicular magnetization. The high-field Hall voltage susceptibility is positive at α=0. Its value decreases with increasing α and changes in sign at α m=20°, which is considered as the easy magnetizable direction of the film. This finding is comparable with those obtained from the magnetization, magnetic force microscopy (MFM) and conversion electron Mössbauer spectra (CEMS) measurements. The obtained LEHE behaviors are rather promising for applications such as magnetic recording heads and magnetic field detectors, where a large output signal is required at low magnetic fields. [Copyright &y& Elsevier]

We propose a system allowing the characterization of thin magnetic multilayer structures that combine conversion electron Mössbauer spectrometry (CEMS) under applied magnetic field with the magneto-optical Kerr effect (MOKE) technique. Measured hysteresis loops obtained from the MOKE part are used for investigation of sample surface magnetic properties. The CEMS part of such a system is suitable for studying the spatial spin distribution during magnetization reversal under applied magnetic field, whose values are established from the measured MOKE loop. The combined technique is demonstrated on the results obtained at 300 K on an exchange-coupled ferrimagnetic amorphous GdFe/TbFe bilayer, where the center of the GdFe layer is enriched in 57Fe. Both techniques confirm in-plane uniaxial anisotropy. The spin structure at the position of the probe layer is analyzed for several values of the external magnetic field applied in the hard magnetization axis direction. [ABSTRACT FROM AUTHOR]

Abstract: The surface and bulk magnetic properties of amorphous FeNbB ribbons in as-quenched state are investigated using various non-destructive methods. The conversion electron Mössbauer spectroscopy has detected the presence of crystalline phase at both surfaces of ribbon sample while the bulk was amorphous. The coexistence of crystalline and amorphous phase was shown also in the X-ray diffraction pattern. Magnetic properties measured by bulk sensitive vibrating sample magnetometer (VSM) strongly differs from the surface characteristics investigated by magneto-optical Kerr effect (MOKE). [Copyright &y& Elsevier]

Abstract: Different natures of the magnetization reversal are studied by means of magnetization and magnetostriction measurements for magnetostrictive “spring-magnet” multilayers of TbFeCo/Fe with a fixed Fe layer thickness of 10nm and variable TbFeCo layer thickness of 12, 16 and 20nm. In such multilayered systems, magnetization reversal occurs at different coercive fields for each layer related to formation of the domain wall at interfaces. The results show that at low temperatures, transition from the ferromagnetic saturation state (with domain walls) to the ferrimagnetic transient saturation state (without domain walls) takes place by the reversal of the magnetic moments in the high-magnetization Fe layers. This process is governed by large magnetic anisotropy of the TbFeCo layer. Increasing temperature, this anisotropy decreases and transition results from the reversal of magnetic moments in the small magnetization TbFeCo layers. Formation of the domain wall at interfaces is clearly evidenced by the negative contribution to the parallel magnetostriction. [Copyright &y& Elsevier]

Exchange-spring TbFeCo/YFeCo multilayers exhibit interesting magnetic and magnetostrictive properties that are rather promising for application in microsystems. In this paper, we present a study of the effect of the exchange coupling on the magnetic properties of these magnetostrictive multilayers. An exchange bias phenomenon, revealed by a shift of the minor hysteresis loop along the applied field axis, is found as the result of the creation of interfacial domain walls. This effect strongly depends on the magnetic properties of the soft YFeCo layer, and becomes more pronounced at low temperatures due to the enhancement of the magnitude of the exchange coupling between the layers. [ABSTRACT FROM AUTHOR]

Abstract: Exchange-coupled multilayered thin films which combine giant magnetostriction and soft magnetic properties are of growing interest for applications. TbFe2/Fe and TbFe2/FeCo nanometric multilayers were grown by RF-sputtering onto glass substrates. A bias field of 250Oe was applied along the longitudinal axis, inducing an in-plane uniaxial magnetic anisotropy. For es-deposited multilayers, TbFe layers are amorphous while soft layers are nanocrystallized. The effect of annealing was investigated by 57Fe Mössbauer spectrometry, magnetic and magnetostriction measurements in the temperature (T ann) range from 150 to 350°C. After annealing, the Mössbauer analysis evidences for an increase of the crystallized iron component, probably due to a thinning of the interfaces. A maximum of the magnetoelastic coefficient is found for T ann around 250°C, with the highest value obtained in the case of TbFe/FeCo. Furthermore, stress relaxation within the film reduces the anisotropy field, leading to a large magnetoelastic susceptibility of about 250MPa/kOe. [Copyright &y& Elsevier]

UHV evaporated (Fe/Y)n multilayers deposited into a MBE evaporator on MgO substrate were investigated by RHEED, GXRD, high-angle XRD, 57Fe Mo¨ssbauer spectrometry at room temperature, and magnetization measurements at 300 and 5 K. The RHEED study was performed for (Fe 15 nm/Y) bilayers as a function of the Y thickness and for two (Fe/Y)n=5 multilayers (tFe=tY=0.5 nm and 1.0 nm) to determine the growth and the nature of the interfaces. The GXRD, high-angle XRD, 57Fe Mo¨ssbauer spectrometry at room temperature, and magnetization measurements studies were performed as a function of the Fe layer thickness (tFe=0.5–6.0 nm) on (Fe tFe/Y 1.0 nm)n>5 multilayers deposited at 300 K. The Mo¨ssbauer paramagnetic doublet obtained at 300 K for tFe=0.5 nm, is characteristic of the Fe–Y interfaces. The crystallization of BCC Fe in the center of the Fe layers occurs for tFe between 0.5 and 1.0 nm indicating that the Fe–Y interfaces are very sharp compared to other deposited (Fe/Y) multilayers. For (BCC Fe/Y) multilayers, the Mo¨ssbauer and the magnetization results indicate that the Fe–Y interfaces thickness remains constant as tFe increases. In average, only one monolayer of Fe is involved at each Fe–Y interface. [Copyright &y& Elsevier]

Machined surfaces of two steels (0.38 and 0.8 wt.% C) were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Mo¨ssbauer spectrometry. Because of the shear and tool wear during the chip formation, a white etching layer appears on these surfaces. X-ray diffraction and Mo¨ssbauer spectrometry data show the presence of retained austenite and suggest the presence of martensite in the white etching layer. The formation of these phases is discussed and from crystallographic data, the temperature reached during turning is estimated. [Copyright &y& Elsevier]

The spin reorientation transition in DyFe11Mo around the spin reorientation temperature (220 K) is investigated by Mo¨ssbauer spectrometry. The temperature dependence of the hyperfine parameters for each Fe site reveals an obvious discontinuity of the hyperfine field. The magnitude of the discontinuity is more important for the 8f site than for the 8i and 8j sites, indicating that the most prominent contribution to the overall anisotropy in the Fe sublattice should be from the Fe ion at the 8f site. This is attributed to the 3d(Fe(8f))–3d(Mo(8i)) hybridization, which may play a quite important role in R(Fe,Mo)12 compounds. [Copyright &y& Elsevier]

X-ray diffraction, high-resolution transmission electron microscopy, Mo¨ssbauer effect and magnetisation investigations have been performed on sputtered Fe0.56Cu0.44 thin films, in which the Fe concentration is near the percolation threshold. Segregation into FCC-Cu rich and BCC-Fe rich phases takes place in the as-deposited film. This state is described in terms of the interfacial transient concentration and ferromagnetism, which originate from the ferromagnetic BCC-Fe in the centre of the individual grains, the iron-rich crystalline Fe(Cu) alloy lying near the interface and the paramagnetic copper-rich FCC-Cu(Fe) matrix. Annealing effects cause not only the evolution of the grain size of the BCC-nanocrystalites, but also the enrichment of Fe in this phase, leading to an increase of the interfacial sharpness. In addition, the magnetic coercive field is found to be enhanced. The coercivity shows a value as large as 24.2 mT for the sample annealed at 400°C. A contribution of the positive surface magnetic anisotropy (KS=+0.1 mJ/m2) to the coercivity is deduced. [Copyright &y& Elsevier]

X-ray diffraction, Mo¨ssbauer effect and magnetisation investigations have been performed on sputtered Fe40(Al2O3)60 thin films. Ultrafine Fe particles of nanometer size in an amorphous Al2O3 matrix have been formed by annealing in the temperature range from 100°C to 500°C. Their particle sizes, however, show a rather wide distribution. Mo¨ssbauer spectra are constituted of both paramagnetic and ferromagnetic contributions. The paramagnetic contribution is associated with small grains of Fe, whereas the magnetic component is contributed by large iron grains. This assumption is supported by the ZFC- and FC-measurements, in which the “blocking” temperatures of 60 and 90 K were evidenced for as-deposited and 200°C-annealed films, respectively. [Copyright &y& Elsevier]

The Fe spin structure in ultrahigh-vacuum-deposited hcp Tb(t[sub Tb])/bcc Fe(t[sub Fe]) multilayers (t[sub Tb] and t[sub Fe] are the Tb and Fe layer thicknesses respectively) with perpendicular magnetic anisotropy (PMA) and large coercivity at low temperatures was investigated by [sup 57]Fe Mossbauer spectroscopy, the polar magneto-optical Kerr effect, and superconducting quantum interference device magnetometry. A spontaneous reversible temperature-driven Fe spin reorientation transition from orientation parallel to the film plane to an out-of plane orientation (with Fe spins tilted by an angle relative to the film normal direction) was observed upon cooling below the reorientation temperature T[sub R]. At a fixed value of t[sub Tb], T[sub R] was found to follow a t[sub Fe][sup -1] behaviour, indicating that the PMA originates from the interfaces. Upon cooling, the perpendicular remanent magnetization shows a step-like increase near the magnetic ordering temperature of Tb, contrary to (T), which exhibits no such anomaly. Apparently, strong coupling of Fe layers via magnetic Tb layers affects the perpendicular magnetic domain structure at remanence. Further, [sup 57]Fe probe layer Mossbauer results concerning structure, composition and Fe spin orientation within Fe-on-Tb and Tb-on-Fe interfaces are reported. [ABSTRACT FROM AUTHOR]

Abstract: The influence of irradiation with high energy Kr ions has been experimentally studied on the magnetostrictive properties of TbFe/Co multilayers. Enhancement of magnetostriction at saturation can be obtained at an optimal fluence with a lower saturation field than for the non-irradiated multilayer. For high fluences, these properties are degraded. [Copyright &y& Elsevier]

Sputtered {Fe/Cr} multilayers with a fixed Cr individual layer thickness tCr=2 nm and variable Fe individual layer thickness (1 nm⩽tFe⩽6 nm) are investigated by means of X-ray diffraction, magnetoresistance and magnetisation measurements. At room temperature, the initial magnetoresistive susceptibility of the as-deposited samples is almost constant. However, the saturation field increases with decreasing Fe-layer thickness, therefore, a maximal magnetoresistance ratio ΔR/R of 0.7% is reached in the sample with tFe=1 nm. After annealing at 350°C, a ΔR/R value as large as 2.3% was obtained. Further annealing causes a reduction of magnetoresistance. As the temperature is decreased, the ΔR/R ratio measured in μ0H=0.3 T increases linearly. At 77 K, the magnetoresistance ratio is about four times larger than that at 300 K. Results are discussed in terms of the scattering located at interfaces and the formation of a ferromagnetic state at high-temperature heat treatments. [Copyright &y& Elsevier]

[Tb(Fe[sub 0.55]Co[sub 0.45])[sub 1.5]/Fe][sub n] and [Tb(Fe[sub 0.55]Co[sub 0.45])[sub 1.5]/(Fe[sub 0.5]Co[sub 0.5]][sub n] multilayers were fabricated by rf-magnetron sputtering from composite targets. Magnetostriction was measured using an optical deflectometer. The as-deposited films showed a soft magnetic and magnetostrictive character, with a coercive field μ[sub 0]H[sub c]=5 mT and a parallel magnetostrictive susceptibility χ[sub λ||]=dλ[sub ||]/d(μ[sub 0]H)=1.4x10[sup -2] T[sup -1]. This magnetostrictive softness was strongly improved by heat treatments: the magnetostrictive susceptibility attains the huge value of 5x10[sup -2] T[sup -1] in applied field of 6 mT. The low-field dependence of the magnetostrictive susceptibility and their technical characters are described in detail. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Sputtered TbCo2/Fe magnetostrictive multilayers have been deposited on both island posts and flat substrates and analysed by laser-assisted tomographic atom probe and 57Fe Mössbauer spectrometry. The three-dimensional reconstructions of the layers were obtained, allowing the analysis of the interfaces. Differences are revealed, as the Fe-on-TbCo2 interface is thinner than the TbCo2-on-Fe interface. This effect is attributed to Fe/Co interdiffusion, controlled by the establishment of the Tb layer. Fe layers are well crystallized. [Copyright &y& Elsevier]

Speeding up and enhancing the performances of nucleic acid biosensing technologies have remained drivers for innovation. Here, we optimize a fluorimetry-based technology for DNA detection based on the concentration of linear targets paired with probes. The concentration module consists of a microfluidic channel with the shape of a funnel in which we monitor a viscoelastic flow and a counter-electrophoretic force. We report that the technology performs better with a target longer than 100 nucleotides (nt) and a probe shorter than 30 nt. We also prove that the control of the funnel geometry in 2.5D using grayscale lithography enhances sensitivity by 100-fold in comparison to chips obtained by conventional photolithography. With these optimized settings, we demonstrate a limit of detection of 4 fM in 30 s and a detection range of more than five decades. This technology hence provides an excellent balance between sensitivity and time to result., (© 2022 Author(s).)

The combination of hydrodynamic actuation with an opposing electrophoretic force in viscoelastic liquids enables the separation, concentration, and purification of DNA. Obtaining good analytical performances despite the use of hydrodynamic flow fields, which dramatically enhance band broadening due to Taylor dispersion, constitutes a paradox that remains to be clarified. Here, we study the mechanism of band broadening in electrohydrodynamic migration with an automated microfluidic platform that allows us to track the migration of a 600 bp band in the pressure-electric field parameter space. We demonstrate that diffusion in the electrohydrodynamic regime is controlled predominantly by the electric field and marginally by the hydrodynamic flow velocity. We explain this response with an analytical model of diffusion based on Taylor dispersion arguments. Furthermore, we demonstrate that the electric field can be modulated over time to monitor and minimize the breadth of a DNA band, and suggest guidelines to enhance the resolution of DNA separation experiments. Altogether, our report is a leap towards to the development of high-performance analytical technologies based on electrohydrodynamic actuation.

The structural and magnetic properties of the evaporated Fe/V multilayers with a fixed V-layer thickness (tV = 1.5 nm) and variable Fe layer thicknesses (0.75 nm < or = tFe < or = 6 nm) have been studied by X-ray reflectivity and high-angle X-ray diffraction, conversion-electron Mössbauer spectrometry, and vibrating sample magnetometry. The results show that multilayers are formed with a broad Fe/V interface and pure crystalline bcc-Fe layers in the center of the individual subsystems. The Fe spin orientation is aligned in the film plane in the individual centers as well in the interfacial regions. The interfacial anisotropy constant Ks was estimated to be equal to 0.04 mJ/m2. This parallel magnetic anisotropy is discussed in terms of reduced symmetry effects on the hybridized 3d states.

One hundred and thirty-eight femoral lengthening operations have been performed in 133 children. The etiology of the shortening was poliomyelitis in 71, infection in 20 and congenital abnormalities in 28. The femur was lengthened in one operative stage by step-cut osteotomy, immediate traction and plate fixation. The mean gain was 35 mm with a maximum of 55 mm. The range of knee movement was unaffected except in 6 cases. Infection occurred in 2 patients without prejudicing the final result. Bony union was obtained in all cases, bone grafting being necessary only once. One permanent sciatic palsy was seen. Thirteen fractures occurred in 9 femurs. Two occurred during operation with loss of lengthening in one case. Eleven occurred post-operatively at the site of osteotomy. One case fractured on 3 occasions. Two cases fractured in another portion of the femur. The complications became fewer with experience and with more accurate technique and it is concluded that the method is safer than progressive lengthening at least in moderate limb length discrepancy.

The delivery of 71 African women who had been circumcised was studied against a control of 781 women who were not circumcised. We have not been able to find any difference as far as caesarean section, forceps delivery or fetal distress in the two groups that were studied. The only difference is a higher frequency of perineal injury in the group of circumcised women.