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The electronic structure of the iron–hydrogen system has been performed in terms of band structure calculation based on the extended Hückel formalism. Heat of formation for a hydrogen atom at octahedral and tetrahedral positions in bcc and hcp iron lattice has been estimated. Allowing the iron lattice to relax, we minimize the energy of the system in terms of a variable lattice parameter. The heat of formation is less endothermic for hydrogen located at tetrahedral interstitial position than for hydrogen at octahedral position. Moreover, the effect of hydrogen is to stabilize the hcp phase. We have performed calculations with different geometrical arrangements, in terms of the distance between hydrogen atoms. Binding energies between hydrogen atoms at nearest and next-nearest interstitial positions are always found unstable. Numerical results obtained in the case of hcp structure are discussed in terms of recent Mössbauer experiments. The physical origin of the sign of the heat of formation in terms of charge transfer is presented. For this we use a model of a Fe4H cluster. [ABSTRACT FROM AUTHOR]

The spin density wave's onset in Cr based superlattices is considered within proximity of Fe interlayer boundaries and the effect of randomly located vacancies in Cr monolayers is examined. The study is performed for Fe/Cr, Fe/Cr/V superlattices with odd and even number of Cr monolayers. It is shown that the number of Cr monolayer determines the spin density wave's nodes onset in the perfect Fe/Cr super lattices. Pinning of Cr magnetic moments on vacancies destroys this determination and leads to appearance or disappearance of nodes. [ABSTRACT FROM AUTHOR]

Presents a study which calculated the local magnetic moments and magnetic orders for a Fe(Cr) monolayer adsorbed on a stepped Cr(Fe)(107) substrate. Results obtained; Presentation of two magnetic arrangements obtained for Cr/Fe(107); Magnetic moment in units of µg per atom.

Effect of surface orientation of nonmagnetic bed material on magnetic properties of the peculiar magnetic adatoms groups (MAGs) is found by simulation. Here we present the results of periodic Anderson model calculations for MAGs on V. The MAGs are formed of the Fe adatoms arranged in triangles, ovals, or short chains and placed over V substrate with (001) or (110) surface orientation. It is shown that magnetism of the Fe-MAGs on V(001) surface can be totally suppressed by the V surroundings, whereas the V(110) surface orientation results in magnetization of the Fe-MAGs and onset of noncollinear atomic moments distribution. Noncollinearity strictly depends on symmetry of the Fe-MAG. [ABSTRACT FROM AUTHOR]

Magnetic moments distribution in Fe 3 Cr n superlattice series with fixed middle Fe monolayer and number of Cr monolayers (MLs) n from 1 to 45 is computed in the framework of collinear and noncollinear Periodic Anderson model. The superlattices are composed of layers in (0 0 1) and (1 1 0) plane with ideal interface. The total energy shows that noncollinear orientation of the magnetic moments remains the ground state for all superlattices with Cr thickness above 5 MLs. Distribution of the magnetic moments for Fe/Cr(0 0 1) superlattices depends on parity of the Cr MLs. For odd numbers Cr magnetic moments are canted and symmetrically distributed between the neighboring Fe slabs. The values of Cr moments are enhanced at the interface and weakened to the bulk in the middle. For even numbers of Cr MLs quasi-helicoidal magnetic moments distribution consisting of two interleaved spirals is found. The moments are screwing sequentially from Fe/Cr interface to perpendicular orientation, keeping the angles and moments for some successive MLs, and then continue screwing towards the next interface. In Fe/Cr(1 1 0) superlattices the magnetic moments of two nonequivalent atoms in the monolayer are canted to each other near Fe/Cr interface and then swing the direction on perpendicular to the fixed Fe moments. [ABSTRACT FROM AUTHOR]

Abstract: Density functional calculations are conducted to investigate the interlayer exchange coupling (IEC) between ferromagnetic Co slabs mediated by a CoSi spacer in Co/CoSi(001) multilayers with CsCl crystalline structure. For both sharp and mixed Co–Si interfaces we calculated the magnetic moment distribution and the energy stability for ferromagnetic (F) IEC and antiferromagnetic (AF) IEC between the Co slabs as function of the spacer thickness. We show that mixing near to the interface noticeably modifies the IEC to the extent that this can change from an oscillatory IEC as function of the spacer thickness to an exponentially decaying AF behavior. [Copyright &y& Elsevier]

Abstract: Objectives: Little is known about the impact of highly active antiretroviral therapy or HIV infection itself on the ovarian function. The aim of this study was to evaluate ovarian function in HIV-infected women in comparison with normal values from non-HIV infected women. Patients and methods: This is a prospective pilot study using markers of ovarian function: the antral follicular count (AFC) defined between cycle days 7 and 10 and follicle-stimulating hormone (FSH), inhibin B and antimüllerian hormone (AMH) for early follicular phase hormonal assessments. A descriptive analysis according to age was performed. Results: Results from 78 HIV positive women are presented. AFC shows a high rate of abnormal values (63 %) occurring surprisingly early. The hormonal markers are concordant with a 36, 57 and 23 % abnormal rate for FSH, inhibin B and AMH respectively. Discussion and conclusion: In our series, HIV seropositivity was associated with stigmas of premature ovarian insufficiency. This may explain impaired fertility but also suggests premature menopause in this population that should therefore be monitored early for such changes. [Copyright &y& Elsevier]

Abstract: The effect of bidimensional Fe clusters and intermixing between the Fe and Cr atoms on the magnetic properties of Fe/Cr superlattices is studied in the framework of collinear and noncollinear periodic Anderson model. Self-consistent calculations performed for the superlattices with Fe layers thicknesses equivalent to 3 and 7Å demonstrate the dependence of the magnetic moments distribution not only on the thickness of Fe layers but on the compositional structure of the interlayers due to different Cr surroundings of the Fe atoms. The superlattices with continuously smooth Fe layers of both thicknesses result in a collinear orientation of Fe and Cr atomic moments. The onset of the Fe clusters and switching on the intermixing of the atoms by a stochastic procedure do not destabilize the collinear orientation for the superlattices with Fe thickness equivalent to 7Å. On the contrary, the superlattices with Fe thickness equivalent to 3Å results in noncollinear orientation of the magnetic moments for the intermixed continuous Fe layers as much as for the Fe clusters in the interlayers before and after intermixing. The clusters are shown have an arbitrary orientation of the average magnetic moments, so that the structure is considered to be a superparamagnetic system. [Copyright &y& Elsevier]

Abstract: Recent studies of x-ray magnetic circular dichroism (XMCD) at V/Co interfaces have determined the magnetic moments on V and Co atoms. The purpose of the present communication is to explain the strong induced polarization on V atoms in thin V layers deposited on Cu substrate and covered by Co atoms. Ab initio calculations performed with abrupt interfaces between Co and V do not lead to agreement with the XMCD results. Interfacial alloying between Co and V atoms increases greatly the moments on the interfacial V atoms and thus improves somewhat the agreement with the XMCD results. [Copyright &y& Elsevier]

Abstract: The electronic structure of 3d transition-metal atoms on face-centered cubic Co(001) substrate is determined within ab initio density functional calculations in the gradient corrected approach. Calculations are performed for ordered surface configuration with coverage equal to 0.25, 0.5, 0.75 and 1ML. For Ni and Fe a ferromagnetic coupling with the Co atoms is always obtained independently of the concentration. Moreover the values of the magnetic moments remain similar. For Mn a ferromagnetic coupling is obtained for low-coverage whereas an in-plane antiferromagnetic coupling is found for a complete Mn overlayer on Co(001). Also, for Sc, Ti, V and Cr a drastic modification of the magnetic map is observed when we go from low-coverage to the monolayer. Cr (Mn) adatoms present antiferromagnetic (ferromagnetic) coupling with Co(001) for x =0.25 whereas an in-plane antiferrimagnetic coupling is obtained for x =1.00. [Copyright &y& Elsevier]

Abstract: We present a theoretical study of the electronic and magnetic structure of the 3d-transition metals (M=V, Cr, Mn and Fe) in several overlayer systems. The electronic as well as magnetic structures are investigated for pseudomorphic overlayers (M/Ir(001)), ordered alloyed overlayers of the type M0.5Ir0.5/Ir(001) and ordered binary surface alloys of V, Cr, Mn and Fe transition metals on Ir(001) substrates. The calculations are performed with a self-consistent tight-binding method using the unrestricted Hartree-Fock approximation within the Hubbard model. We obtained metastable c(2×2) configurations for V, Cr and Mn and a p(1×1) configuration for Fe pseudomorphic overlayers. However, ferrimagnetic configuration has been obtained for the ordered surface alloys M0.5Ir0.5 and the binary alloyed overlayers on Ir(001) surfaces. [Copyright &y& Elsevier]

Abstract: Magnetic moment distribution in Cr(001) and Cr(110) films with strips and random defects at surface are calculated in the framework of a periodic Anderson model. All Cr(001) films reveal an appreciable surface magnetic moment the value of which depends on the type of defect. The film with flat Cr(110) surface does not exhibit any magnetization because of an equal number of atoms with opposite moments. Only well-ordered defects like one atom strips can give a noticeable magnetization in Cr(110) films. [Copyright &y& Elsevier]

Abstract: Ab initio density functional theory is used for the determination of the electronic and magnetic properties of XGe2 (X=Mn, Fe, Co) ordered compounds. FeGe2 displays an antiferromagnetic ground state with Fe magnetic moment of 1.43 μ B and a ferromagnetic configuration a few mRy above. For MnGe2 it is difficult to see whether the ground state is non-magnetic or antiferromagnetic because the difference of energy between them is marginal. The ferromagnetic configuration is metastable but a slight increase of the lattice parameter stabilizes it. No magnetic configuration is obtained for CoGe2 even with a slight increase of the lattice parameter. We report also some preliminary results of germanium based compounds with two different chemical types chosen between Mn, Fe and Co. The magnetic arrangements obtained are correlated to the relative positions of the magnetic atoms. [Copyright &y& Elsevier]

Abstract: The collinear magnetic structure of n (n =1, …, 6) monolayers (ML) of Fe films deposited on Co(111) substrate is investigated by ab initio density functional theory within a generalized gradient approximation. We have found that the ferromagnetic ground state exists only for one Fe monolayer. For higher thickness, a sequence of antiferromagnetic coupling with low magnetic moments in the inner layers of films is identified as ground state. [Copyright &y& Elsevier]

We discuss the polarization of V atoms on Co(001) substrates within density functional calculations. For sub-monolayer coverage the coupling between V and Co is clearly of antiferromagnetic type whereas it changes to ferromagnetic coupling in the case of a full V monolayer on Co(001). The results obtained in the case of a sub-monolayer coverage are in agreement with recent X-ray magnetic circular dichroism by Huttel et al. [Phys. Rev. B 68, 174405 (2003)]. The transition from antiferromagnetic coupling (in the case of sub-monolayer coverage) to ferromagnetic coupling (for a full monolayer coverage) is discussed in terms of local coordination numbers and V-Co hybridization. Comparison with Cr and Mn coverages on Co(001) complicates the problem: i) submonolayer Cr coverage stabilizes the antiferromagnetic coupling between Cr and Co atoms (like for V on Co(001) whereas a Cr monolayer on Co presents in-plane antiferromagnetic coupling; ii) submonolayer Mn coverage stabilizes now the ferromagnetic coupling between Mn and Co whereas a Mn monolayer on Co(001) presents an in-plane antiferromagnetic coupling. Competition between Co induced magnetism and surface induced magnetism at V sites is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Electronic and magnetic properties of bulk and films of FeGe2 are investigated within ab initio density functional theory. Bulk structure displays an anti-ferromagnetic ground state with Fe magnetic moment of 1.36μB and a ferromagnetic configuration a few mRy above. Thin films with a few monolayers display a ferromagnetic ground state with a metastable anti-ferromagnetic configuration a few mRy above. A transition from ferromagnetism to anti-ferromagnetism is observed when the thickness of the film is increased. A strong increase of the magnetic moments, up to 2.64μB, on Fe atoms present at the surface is observed. [Copyright &y& Elsevier]

A self-consistent tight-binding method has been used to calculate the electronic structure and magnetic properties of Pd islands on Ag(0 0 1) surface. We find a paramagnetic state for 21 Pd atoms ordered on one layer, whereas 33 atoms ordered on two atomic layers display a net magnetic moment. Surface effect and low atomic coordination do not lead necessarily to the onset of magnetism in Pd. More precisely, the present results show that the formation of the cluster (thickness and atomic aggregation) is one of the most important factor which could determine the magnetism of Pd systems. [Copyright &y& Elsevier]

Recent X-ray magnetic circular dichroism and magneto-optical Kerr effect performed by Matthes et al. [J. Appl. Phys. 93 (2003) 6504] on in situ layered systems of fcc Co and FeMn epitaxially grown onto Cu(0 0 1) templates as well as Co/FeMn/Co trilayers display very interesting results. Measurements showed that the magnetic moment on Fe is parallel to the Co magnetization direction whereas, for Mn the XMCD signals are small. In order to explain this behavior ab initio density functional calculations on (Fe0.5Mn0.5)n/Co(0 0 1) and Co/(Fe0.5Mn0.5)n/Co(0 0 1) have been performed for n varying from 1 to 3. Within generalized gradient corrections the Fe–Mn interfacial alloy, one monolayer thick on Co(0 0 1), with ferromagnetic coupling between Fe and Mn corresponds to the ground state whereas the same Fe–Mn monolayer in Co/FeMn/Co presents a magnetic moment of Mn opposite to that of Fe and Co. For all systems investigated we obtain a ferromagnetic polarization between Fe and Co atoms in agreement with the XMCD results. The behavior of the Mn polarization is more complex: an antiferromagnetic polarization between Mn atoms in nearest neighboring FeMn alloy plane is always obtained. [Copyright &y& Elsevier]

The magnetism is investigated for pseudomorphic monolayers of (V, Cr and Mn) and their substitutional c(2 × 2) alloyed structures adsorbed on Pt(0 0 1) semi-infinite surfaces using the semiempirical tight-binding method. Vanadium pseudomorphic monolayer exhibits a c(2 × 2) magnetic ordering, whereas Cr and Mn overlayers exhibit both c(2 × 2) and p(1 × 1) magnetic structures. The substitutional alloyed overlayers exhibit ferrimagnetic structures that leads to appreciable net surface magnetization. [Copyright &y& Elsevier]

The phase of the short-range interlayer exchange coupling oscillations in Fe n Cr m superlattices is expressed in terms of the intermixing at the Fe-Cr as well as at the Cr-Fe interfaces. The interdiffusion is modeled through stochastic algorithms, which presupposes floating of the atoms on the surface of the sample during the epitaxial growth. It automatically leads to the different chemical and magnetic structure of Fe on Cr and Cr on Fe interfaces. Self-consistent calculations of the magnetic moments are performed on the basis of the periodic Anderson model. Although short-range (2 monolayers (ML)) oscillations of exchange coupling were detected for all considered structures, its amplitude and phase strongly depend on the interface alloying. Introduction of the same intermixing at both interfaces does not change the phase as compared to the ideal superlattices with sharp interfaces. However different interdiffusion leads to the π-phase shift in accordance with experimental results for the Fe-Cr-Fe trilayers grown on an Fe whiskers. Distribution of magnetic moments on Fe atoms contains several distinct peaks but their position and relative area weakly depend on the alloying and interlayer exchange coupling in the superlattice. On the contrary, magnetic moments on Cr atoms are very sensitive to the intermixing and their behavior determines the strength and the phase of exchange coupling oscillations. [ABSTRACT FROM AUTHOR]

The magnetism of Fe monolayers (MLs) adsorbed on Ir surfaces at low- and high-index orientations is investigated using a semi-empirical tight-binding method using the Hartree–Fock approximation within the Hubbard Hamiltonian. Iron MLs adsorbed on Vicinal Ir surfaces exhibit net magnetization close to that of (1 0 1) orientation. The maximum local magnetic moment is obtained at the edge atom, whereas the least is at the kink due to the coordination. Ferromagnetic (FM) 3d–5d coupling between Fe and Ir is obtained in agreement with experimental results and theoretical predictions. The filling of the 5d band is behind the kind of coupling as compared with Fe MLs adsorbed on W substrates and other elements less than half-filled in the series of transition. [Copyright &y& Elsevier]

We present ab initio calculation of the electronic structure and magnetic properties of Fe/Re multilayers assuming hcp crystallographic phase. The system is modeled according to recent structural analysis which shows that Fe/Re has bct(0 0 1) ordering for 0⩽tRe⩽8 A˚ after which a structural phase transition occurs to an hcp phase. Antiferromagnetic and ferromagnetic orders appear more stable than the nonmagnetic (NM) state, only when the Fe atoms begin to adopt an expanded volume of about 27% accompanied by an axial distortion (c/a=1.42). The sizeable magnetic moments calculated on Fe atoms contrast with the paramagnetic bulk hcp. These results are discussed and compared with recent experimental data on hcp Fe/Re superlattices and also with magnetic properties of Fe/Ru multilayers. [Copyright &y& Elsevier]

X-ray magnetic circular dichroism (XMCD) as well as magneto-optic Kerr effect display a ferromagnetic coupling at the Mn–Co interface followed by a non-ferromagnetic signal when the thickness of the Mn film on Co(0 0 1) increases. Ab initio density functional with gradient corrections (GGA) can explain this behavior. Within GGA the Mn–Co interfacial alloy with ferromagnetic coupling between Mn and Co is shown to be the ground state. Adding one and two Mn monolayers on it leads to a complex non-ferromagnetic behavior with high magnetic moments on the Mn atoms. As a result of this complex non-ferromagnetic behavior, the Mn mean magnetic moment decreases dramatically for one Mn monolayer and tends to zero for two Mn monolayers in quantitative agreement with the XMCD results. [Copyright &y& Elsevier]

The magnetization of a Fe monolayer on stepped W substrates is investigated using tight-binding method with the Hartree–Fock approximation within the Hubbard Hamiltonian. To assert the validity of the parameters of the Model Hamiltonian we first determine the magnetization of low miller indices and make the comparison with the full-potential calculations when available. The stepped surfaces net magnetization of Fe overlayers on W is enhanced from that of the (0 0 1) orientation owing to its geometry. This enhancement ranges roughly from 10% to 20% as compared to the bulk value. An antiferromagnetic coupling between the Fe atoms at the surface and those of W in the subsurface is always present in all the considered cases. [Copyright &y& Elsevier]

We present a detailed study of oxygen contamination on the structural and magnetic properties for both Fe/MgO(001) substrate and MnPd bilayer grown on Fe/MgO(001) by using a plane wave self consistent field (PWscf) method based on DFT and DFT+U approaches, where a generalized gradient correction for exchange-correlation potential is taken into account. For the clean ( Mn 0.5 Pd 0.5 ) 2 bilayer grown on Fe/MgO(001) substrate, we have found that the c(2x2)-MnPd/c(2x2)-MnPd arrangement, where the magnetic moments of the Mn (Pd) atoms belonging to the surface and subsurface of 4.61 (0.05 μ B ) and -4.03 (0.21 μ B ), is lowest in energy than the c(2x2)-MnPd/p(1x2)-MnPd, p(1x2)-MnPd/MnPd-c(2x2) and p(1x2)-MnPd/p(1x2)-MnPd arrangements. A ripple is obtained at the surface (subsurface) plane. The contamination by O (1-ML coverage) on top for both Fe/MgO(001) and MnPd/Fe(100) multilayers increases interlayer distances between the surface and subsurface layers, with a preferential adsorption of oxygen atoms on the fourfold hollow sites when both DFT and DFT+U approaches are used. Similar magnetic ordering is obtained for Fe/MgO(001) and O/Fe/MgO(001) as well as for (MnPd) n /Fe(100) and O/(MnPd) n /Fe(001) sytems, where n=1-2, taking into account both approaches. The DFT+U approach produces an enhancement of the magnetic moments but does not modify the magnetic ground states of those systems. Here, we found that one half of oxygen atoms is pushed out-of-plane while the other half penetrates the MnPd (Fe) surface, giving rise to the MnO (FeO) oxide surface, in agreement with available experimental data. [ABSTRACT FROM AUTHOR]

Abstract: Huttel et al. (Phys. Rev. B 68 (2003) 174405) using X-ray magnetic circular dichroism have depicted an induced magnetic moment for V atoms deposited on FCC Co(001). In the present communication, we discuss the onset of magnetic polarization of very thin V films atop Co(001) within classical density functional theory. Both local density approximation and gradient corrected approaches are used. For one V monolayer on Co(001), a ferromagnetic coupling is obtained whereas for thicker V slabs, an antiferromagnetic-like behavior is shown to be the ground state. It is clearly shown that the Co-induced polarization on V atoms is short-ranged and mainly limited to the Co–V interface. A very different magnetic behavior is observed when alloying at the V/Co interface is present. [Copyright &y& Elsevier]

Studies theoretically and experimentally the structural properties of manganese (Mn) films with a thickness of one monolayer deposited on a Ag(100) substrate. Investigation of the magnetic structure of these films and the effect of magnetism on their relative stability; How a complete inversion of the Mn ML can be obtained; Examination of the energetic stability of an on-top Mn ML againts the formation of an inverted Mn ML.

Presents a study of the magnetic properties of compact chromium clusters deposited on iron. Tight-binding calculation results; Difference between the band energy of both magnetic configurations; Model of the magnetic interactions with a two-parameters Ising model.

Presents a study that discussed antiferromagnetic coupling between nearest neighbor vanadium atoms in the case of free-standing cluster and slabs at the surface of vanadium and vanadium island on silver. Onset of magnetism in terms of the exchange integral J; Various possible magnetic states; Characterization of the transition from nonmagnetic to magnetic order.

Presents a study that observed antiferromagnetic coupling between iron and vanadium atoms at the iron/vanadium and iron/chromium interfaces. Magnetic moments of the atoms in Fe[sub3]V[subn] slabs along (001); Results of the calculations of the magnetic moments of the iron/chromium system.

We have investigated the adsorption sites and the electronic structure correlated with the magnetic properties of ultrathin Fe films on W(110) system using spin-polarized calculations within the density-functional approach with generalized gradient approximation by the pseudopotential plane-wave code. For one Fe monolayer (ML) on W(110) system the Fe atoms prefer to bind on the bridge adsorption sites of the W(110) surface, with an inward relaxation of 12.68%. The top and diagonal bridge sites investigated are energetically less favorable. We have shown that intermixing between Fe and W is unlikely: the surface ordered Fe-W alloy is unstable against the 1-ML Fe on W(110). While the control of oxygen element is known to be an important key to a perfect growth of Fe on W(110), its possible contamination is checked. Performing spin polarized calculations with the optimized geometry, the induced magnetic moments on W subsurface are obtained: the W atoms are always antiferromagnetically coupled to the Fe atoms, one exception being the case of the antiferromagnetic Fe surface where, due to frustration, the induced polarization on the W atoms is zero. The bridge site is the lower adsorption energy one for O2 molecular bonding perpendicular to the surface. In the case of O2 bonding parallel and oblique to the surface, it is always dissociated into two O atoms on Fe/W(110) surface through geometry optimization, for all considered sites. [ABSTRACT FROM AUTHOR]

Structural and magnetic properties of ultrathin films MnPd/Fe grown on MgO(001) are investigated using a self-consistent pseudopotential plane waves method based on density functional theory in the Perdew–Burke–Ernzerhof generalized gradient approximation. The results obtained reveal the presence of an antiferromagnetic coupling between successive Mn [100] rows, combined with a ripple where Mn outward atoms exhibit a positive magnetic moment, in the case of Mn overlayer on Fe/MgO(001). In the case of MnPd monolayer ordered alloy, the c (2 × 2) structure formation is more favorable than the p (1 × 2) one, exhibiting a ferromagnetic coupling between Mn neighbor atoms with a positive induced ferromagnetic moment on Pd atoms. Pd atoms are pushed outward. For 1-ML Mn x Pd 1 − x on Fe/MgO, the Mn absolute mean magnetization per atom increases as x coverage increases, whereas the Pd mean induced magnetic moment decreases. For systems alternating Mn and Pd monolayers on Fe/MgO(001), a complex magnetic structure is shown on Mn monolayers: changing from Mn neighboring antiferromagnetic coupling to Mn [010] rows antiferromagnetic behavior. The correlation is made between the electronic structure and the magnetic properties, by comparing filled with partially filled components (Pd, Mn and Fe) d -bands. The magnetization easy-axis changes between the in-plane and the out-of-plane orientations from Fe/MgO to MnPd/Fe/MgO systems. [ABSTRACT FROM AUTHOR]

LEED experiments by Offi et al. (Phys. Rev. B 66 (2002) 064419) have recently revealed that the Fe50Mn50 alloy thin films keeps the FCC structure when growing on Cu(0 0 1) and on Co/Cu(0 0 1). Stability of magnetic configurations of Fe50Mn50 alloy monolayer film is investigated using ab-initio calculations within density functional theory with gradient corrections. Fe induced magnetic moment of 2.85 μB with Mn magnetic moment of 3.61 μB aligned parallel with the ferromagnetic moment of the Co layer have been found as groundstate configuration with the Perdew–Wang functional in agreement with X-ray magnetic circular dichroism results. [Copyright &y& Elsevier]

Following experimental works of Wuttig et al. (Phys. Rev. Lett. 70 (1993) 3619) and O''Brien and Tonner (Phys. Rev. B 51 (1995) 617) very Mn thin films overlayers on Ni(0 0 1) have been investigated through ab initio density functional theory with generalized gradient corrections. A relaxed two-dimensional Mn0.5Ni0.5 ordered surface alloy shows evidence of ferromagnetic metastable solution in reasonable agreement with experimental results. [Copyright &y& Elsevier]

Magnetism of Mn single atom and dimer on Co(0001) hcp surface is studied on the basis of density functional theory using Quantum Espresso code. The most stable geometry takes place when Mn is adsorbed in the most highly coordinated sites. Mn single atom couples ferromagnetically to the Co atoms and shows a high magnetic moment of 4.53 μ B . Mn dimer also couples ferromagnetically to the Co atoms, shows a mean atomic magnetic moment of 4.45 μ B , and increases its interatomic distance to minimize its energy. [ABSTRACT FROM AUTHOR]

Objectifs Evaluer l’apport de l’immunologie, de l’histologie et de l’ostéodensitométrie après réintroduction du gluten. Patients et méthodes 300 enfants atteints de maladie cœliaque :anticorps anti- transglutaminase, anti-endomysium positifs, l’histologie : stade IIIc, phénotype : HLA DQ2/DQ8, ont bénéficié d’un suivi de 16 ans ap. Annuellement : auxologie, taux d’hémoglobine. Tous les 6 ans : Biopsie jéjunale et ostéodensitométrie. Tests statistiques : SPSS 16.0, Graphpad prisme 5. Résultats Groupe I : 130 patients (43,3%) : Evolution silencieuse : Anticorps anti-transglutaminase positifs à 18 U/ml, anti-endomysium positifs au1/10, atrophie villositaire modérée corrélée aux antitansglutaminase p<0,0001 et aux anti-endomysium p<0,0001, sans signes de carence. Groupe II : 95 patients (31,7%) : Evolution latente : 55,7% étaient positifs pour les antitransglutaminase et négatifs pour les anti- endomysium, 13,3% étaient négatifs pour les antitransglutaminase et positifs pour les anti-endomusium avec une concordance : kappa=0,89, histologie stade I, sans signes de carence. Groupe III : 75 patients (25%) : bilan normal. Conclusion La tolérance au gluten peut s’installer avec l’âge après un régime strictement suivi. [ABSTRACT FROM AUTHOR]

Abstract: First-principle band structure calculations on (Mn0.5Pd0.5) n /Co(001) and Mn x Pd1− x /Co(111) systems are carried out by a plane wave self consistent field (PWscf) method, where a generalized gradient correction for exchange-correlation potential is taken into account. For the Mn0.5Pd0.5 monolayer on Co(001), magnetic moments per surface atom of 4.23 μB and 0.34 μB are obtained for Mn and Pd, respectively, and a ripple is shown at the surface plane. Those magnetic moments are aligned parallel to the total moment of Co(001). A MnPd layered antiferromagnetic sequence with a ferromagnetic coupling between Mn (Pd) atoms at the interface and Co film is obtained for (Mn0.5Pd0.5) n /Co(001), n =1–3, associated with a Pd outward buckling at the surface layer. Investigations of Mn x Pd1− x monolayer on Co(111) have shown that the crystallographic orientation does not modify significantly neither the magnetic moments of Mn and Pd atoms nor their ferromagnetic coupling with the Co(111) substrate, except for x =0.50 and 0.75, where the Mn sub-lattice presents an antiferromagnetic coupling leading to a quenching of the Pd magnetic moment. A corrugation surface is also shown. The correlation is made between the electronic structure and the magnetic properties, by comparing filled with partially filled components (Pd, Mn, and Co) d-bands. [Copyright &y& Elsevier]

La plupart des maladies chroniques interfèrent avec les processus de croissance surtout en période de maturation pubertaire. Mais si la maladie chronique altère la croissance et retarde le développement de la puberté, cette dernière par l’absence de secrétions en hormones stéroïdiennes l’aggrave. Objectif: Rapporter notre expérience sur la supplémentation en hormones de croissance et stéroïdiennes au cours de quelques maladies chroniques. Matériel et Méthodes: Pour chaque pathologie deux lots de 10 enfants âgés entre 10 et 14 ans ont été tirés au hasard. Un groupe I non supplémenté en hormone de croissance et hormones stéroïdiennes et un groupe II supplémenté. Résultats: Des corrélations positives ont été établies entre la sévérité des signes clinique, la durée du traitement et le retard de croissance. Le traitement hormonal a permis une accélération de la vitesse de croissance et le déclenchement de la puberté chez certains enfants. Conclusion: Ainsi maladie chronique et retard pubertaire à l’adolescence doivent être traités en même temps. [ABSTRACT FROM AUTHOR]

Contrairement à l’adulte où le vieillissement est progressif, chez l’enfant il peut être accéléré… C’est la mutation au niveau du gène LMNA qui est responsable de la sénescence. Object: comparer les mécanismes de la sénescence de l’enfant de l’adulte et leurs conséquences. Patients et Méthodes: Chez ces 8 enfants ont été analysé l’aspect clinique, le poids, la taille, l’âge osseux, la vitesse de croissance, l’âge de la puberté, analyse génétique. Résultats: L’âge moyen au moment du diagnostic était de 24 mois pour les filles et de 18 mois chez les garçons. Tous avaient une peau ridée, des cheveux blancs clairsemés, un retard de la prise pondérale et de la vitesse de croissance, des signes d’ostéoporose, une mutation G6O8G ou Zmpste. Tous sont décédés entre 12 et 15 ans. Conclusion: La Progéria est une maladie autosomique dominante congénitale ou acquise par mutation de novo. Actuellement le traitement est peut être possible :grâce à l’association des statines et des biphosphonates,. [ABSTRACT FROM AUTHOR]

Abstract: The non-collinear magnetic moment distribution at the Cr/Fe(110) interface of an Fe(110) thin film covered by a Cr monolayer is revealed by means of periodic Anderson model calculations. It is shown that the Cr surface has two magnetically non-equivalent sites with magnetic moments canted to each other. The Fe atoms in the subsurface monolayer also acquire two magnetically non-equivalent sites with magnetic moments canted to each other. Non-collinearity is shown to be a ground state for the Cr/Fe(110) multilayer. [Copyright &y& Elsevier]

Abstract: We investigate the magnetic properties of V/Co interfacial systems and adatoms within the density functional theory taking into account the structural relaxation. The hybridization between the V and Co orbitals results in a V magnetic moment induced by the surrounding Co atoms. The ground state V magnetic moment magnitudes range from ~0 to 2.17 μB/atom depending on the specific local environment. [Copyright &y& Elsevier]

Abstract: We present ab initio density functional calculations of the electronic structure and magnetic properties of X 2/Cr36(001) and X 1/Cr37(001) multilayers, with X =Sn, V and Mn, to investigate the impact of the proximity effects of the X layers on the spin density waves of the Cr slab. We find different magnetic profiles corresponding to the spin density wave and to the layered antiferromagnetic configurations. The nature of the different magnetic solutions is discussed in terms of the different interfacial environments in the proximity of Sn, V or Mn. The magnetic behavior at the interface is discussed in connection with the electronic structure through the density of electronic states projected at the interfacial X and Cr sites. We compare the results with those previously obtained for Fe3/X 1/Cr37/X 1(001) multilayers to analyze the role played by the ferromagnetic iron slab. [ABSTRACT FROM AUTHOR]

Abstract: Electronic and magnetic properties of ultra-thin films of compounds have been investigated using ab initio density functional theory (DFT). In the bulk environment we obtained anti-ferromagnetic coupling between Fe atoms and no magnetic polarization on Ge atoms. Besides this ground state configuration a metastable solution is obtained with a ferromagnetic coupling between Fe atoms and anti-ferromagnetic coupling between Fe and Ge. Concerning the thin films, the magnetic coupling between Fe atoms depends on the film thickness. Ferromagnetic order is obtained in the case of an ultra-thin film and a transition to anti-ferromagnetic coupling is observed when we increase the film thickness. [ABSTRACT FROM AUTHOR]

Abstract: Density Functional Theory calculations have been performed on a skeletal isomerization of n-butane into isobutane in the absence and presence of hydrogen on a Pt (100) ultra thin film. A pathway implying monomolecular mechanism for the isomerization is assumed. A cyclic type mechanism is induced by the absence of hydrogen while a bond-shift mechanism is favored by its presence. Also, the presence of hydrogen facilitates isomerization by decreasing the energy barrier from 3.41eV to 2.77eV. The platinum thin film surface essentially acts as a hydrogen attractor. Afterwards the internal rearrangement of atoms of the activated hydrocarbons results in isomerization. [Copyright &y& Elsevier]

Abstract: The magnetic map of thin FeMn film deposited on Cu surfaces is determined within ab initio density functional approach. Those films made of ordered equiatomic alloys present various type of magnetization depending drastically on their thickness. Interlayer exchange coupling through the Cu spacer depends on two quantities which are the number of atomic layers in the magnetic film as well as the thickness of the Cu spacer. The results obtained show evidence of the interlayer exchange interaction in antiferromagnetic/nonmagnetic/antiferromagnetic system which could be attributed to the confinement of the electronic states in the nonmagnetic spacer through the presence of scattering potentials and the quantum mechanical exchange interaction similarly to that found classically in the ferromagnetic/nonmagnetic/ferromagnetic trilayers. [Copyright &y& Elsevier]

• Effect of oxygen on the magnetization of Fe/Mn multilayers. • DFT + U calculations on the stability of Fe/O/Mn/Fe(001) multilayers. • The interlayer exchange coupling (IEC) is O-dependent. • This modification of IEC can be related to strong variation of LDOS. [Display omitted] Zenia et al. (Surface Science 584 (2005) 146152) have shown that a Mn monolayer on Fe(001) is in-plane antiferromagnetic. They have also obtained a ferromagnetic as well as an antiferromagnetic coupling between Mn and Fe in the subsurface layer but those couplings are found higher in energy. When an oxygen monolayer is added this in-plane antiferromagnetic solution becomes unstable. Besides Meza-Aguilar and Demangeat (Eur. Phys. J. B 93 (2020) 107 have shown that the interlayer exchange coupling in Fe/Cr/Fe(001) can be modified by the inclusion of one monolayer of oxygen i.e. O/Fe/Cr/Fe(001). In the present communication, we study the magnetic stability of a Mn monolayer on Fe(001) and the interlayer exchange coupling in Fe/O/Mn/Fe(001) and O/Fe/Mn/Fe(001) multilayers with a DFT+U scheme. The Fe/O/Mn/Fe(001) multilayer is energetically clearly unstable and convergency leads to the displacement of the oxygen monolayer on top of the Fe surface atoms so that we restrict ourselves to the determination of the magnetic map of O/Fe/Mn/Fe(001). The interlayer exchange coupling in Fe/Mn/Fe(001) is modified by adding a monolayer of oxygen atoms on it. This is very similar to the result obtained recently on Fe/Cr/Fe(001) multilayers. [ABSTRACT FROM AUTHOR]

Abstract: The possibility of tailoring the spin density waves in Fe/Cr(001) multilayers through the selective inclusion of Sn, V and Mn monolayers is investigated with the density functional tight-binding linear muffin-tin orbital method in the generalized gradient approximation of the exchange and correlation potential. Despite the non-magnetic character of Sn and V when substituting Cr atoms located at the nodes, the modifications induced on the spin density waves are important due to the strong hybridization. In general we find that V modifies drastically the global features of the spin density waves leading to the onset of a magnetically dead region in the Cr spacer whereas Mn inserted at the nodes rather destroys the density wave working in favor of stabilizing the layered antiferromagnetic structure. The trends obtained are consistent with experimental data when available. Since both the magnetic profile and the position of the nodes at the spacer can be modified, the present results are relevant in the context of the spin-dependent transport through magnetic multilayers in which the magnetoresistance will vary if the scattering regions across the transport direction are modified. [Copyright &y& Elsevier]

We present ab initio calculations of the exchange coupling for Co/Ir systems using a self-consistent full-potential linearized augmented plane-wave (FLAPW) method. The local spin density approximation (LSDA) as well as the generalized gradient approximation of (GGA) are used to treat the exchange correlation potential. Structural optimization is considered for all systems due to the size difference between Co and Ir atoms. We obtain an oscillatory behavior for the interlayer exchange coupling with a period of 5.83 Å, for both LSDA as well as GGA-PBE. The first antiferromagnetic peak is found for an Ir spacer of thickness 3.74 Å, with strength of J = 51.09 mJ/m2 for the GGA-PBE and 37.00 mJ/m2 for the LSDA. [ABSTRACT FROM AUTHOR]

Abstract: Using DACAPO code based on density functional theory (DFT) with plane wave basis set, the ionic cores being represented by ultra soft pseudo-potentials, and TB-LMTO-ASA method, we investigate the polarisation of Fe films on Co(110) substrate. Calculations with and without relaxation were carried out. We found that up to three Fe monolayers, a ferromagnetic order is the ground state. However, an antiferromagnetic coupling between Fe monolayers is observed for thicker films. A comparison between the results obtained for up to three Fe monolayers by both methods is reported. [Copyright &y& Elsevier]