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Interfacial magnetoelectric coupling is a viable path to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO 3 system, only tiny changes of the interfacial Fe magnetic moment upon reversal of the BaTiO 3 dielectric polarization have been predicted so far. Here, by using X-ray magnetic circular dichroism in combination with high-resolution electron microscopy and first principles calculations, we report on an undisclosed physical mechanism for interfacial magnetoelectric coupling in the Fe/BaTiO 3 system. At this interface, an ultrathin oxidized iron layer exists, whose magnetization can be electrically and reversibly switched on and off at room temperature by reversing the BaTiO 3 polarization. The suppression/recovery of interfacial ferromagnetism results from the asymmetric effect that ionic displacements in BaTiO 3 produces on the exchange coupling constants in the interfacial-oxidized Fe layer. The observed giant magnetoelectric response holds potential for optimizing interfacial magnetoelectric coupling in view of efficient, low-power spintronic devices. Interfacial magnetoelectric coupling could lead to a new generation of memory devices. Here, Bertacco and colleagues observe a large electric-field switchable magnetoelectric coupling effect in iron/barium titanate heterostructures, which is due to a thin oxidized iron layer.

The search for novel tools to control magnetism at the nanoscale is crucial for the development of new paradigms in optics, electronics and spintronics. So far, the fabrication of magnetic nanostructures has been achieved mainly through irreversible structural or chemical modifications. Here, we propose a new concept for creating reconfigurable magnetic nanopatterns by crafting, at the nanoscale, the magnetic anisotropy landscape of a ferromagnetic layer exchange-coupled to an antiferromagnetic layer. By performing localized field cooling with the hot tip of a scanning probe microscope, magnetic structures, with arbitrarily oriented magnetization and tunable unidirectional anisotropy, are reversibly patterned without modifying the film chemistry and topography. This opens unforeseen possibilities for the development of novel metamaterials with finely tuned magnetic properties, such as reconfigurable magneto-plasmonic and magnonic crystals. In this context, we experimentally demonstrate spatially controlled spin wave excitation and propagation in magnetic structures patterned with the proposed method. Thermally assisted magnetic scanning probe lithography is used to reversibly pattern magnetic anisotropy landscapes in a continuous exchange-bias system, where propagating spin waves are excited.

We report on the chemical and electronic properties of epitaxial Fe/MgO/Ge(001) heterostructures probed by X-ray Photoemission Spectroscopy. At variance with the Fe/MgO/Fe system, annealing at 570 K produces a sizable interdiffusion at the upper Fe/MgO interface, while at 470 K this process is inhibited. The XPS analysis of band alignment in heterostructures annealed at 470 K grown onto an intrinsic Ge substrate indicates that the Fermi level is placed at the center of the MgO gap and that the Schottky barrier height is 0.35±0.1 eV, thus indicating a partial depinning of the Fermi level.

The bond-order potentials (BOPs) idea employs the orthogonal two-centre tight-binding (TB) representation for the bond energy and the Harris-Foulkes approximation for the repulsive pairwise contribution. In the last ten years, although many efforts have been focused on theoretical calculations of the bond order expression, the BOPs still suffers from the uncertainty of how best to choose the semi-empirical TB parameters that enter the scheme. In this paper, we review recent developments to obtain the reliable and transferable BOPs which help to extend the accuracy and applicability to technologically important multi-component systems. Firstly, we have found that a simple pair potential is unsuitable for describing the environmental screening effects due to thes andp orbital overlap repulsion in transition metal alloys and therefore the inability to reproduce the negative Cauchy pressures exhibiting in strong covalent systems. By adding the environmental dependent repulsive term, the Cauchy pressure problem has been removed and we are now able to get the BOPs for studying dislocations, extended defects and mechanical properties of high-temperature intermetallic Ti-Al alloys. In particular, new results on the core structures and possible dissociation of different type of dislocations will be discussed. Secondly, we present the first derivation of explicit analytic expressions for environmental dependence of σ,π and δ bond integrals by inverting the non-orthogonal matrix. We illustrate the power of this new formalism by showing that it not only captures the transferability of bond integrals between Mo, Si and MoSi2 but also predicts the large discontinuities between first and second nearest neighbours forppσ, ppπ andddn even though absence of any discontinuity for theddσ bond integral. A new environmentally dependent BOPs has been developed forbcc-Mo indicating that the core structure of l/2 screw dislocations is narrower than structures found in previous studies in agreement with recentab initio calculations. Finally, the new formalism will allow us to study the problem of medium range order found recently in amorphous materials with covalent bonding at large and realistic nanoscale. For the case ofa-C where the issue ofsp2 vssp3 is very crucial for modelling amorphous structure we found that the σ and π bond integrals are not only transferable between graphite and diamond structures but they are also strongly anisotropic due to inter-plan bonding between graphite sheets.

Aberration correction in the scanning transmission electron microscope combined with electron energy loss spectroscopy allows simultaneous mapping of the structure, the chemistry and even the electronic properties of materials in one single experiment with spatial resolutions of the order of one Ångström. Here the authors will apply these techniques to the characterization of epitaxial Fe/MgO/(001)Ge and interfaces with possible applications for tunneling junctions, and the authors will show that epitaxial MgO films can be grown on a (001)Ge substrates by molecular beam epitaxy and how it is possible to map the chemistry of interfaces with atomic resolution.

A number of postulated in-vessel loss of coolant accidents (LOCAs) associated with the first wall and baffle cooling systems of the ITER detailed design have been analyzed for the ITER Non-site Specific Safety Report (NSSR-1). A range of break sizes from one first wall tube break (1.57 × 10−4 m2) to damage to all in-vessel components (0.6 m2 break) have been examined. These events span the ITER event classification from likely events to extremely unlikely events. In addition, in-vessel pipe breaks in combination with bypass of the two confinement barriers through a generic penetration have been examined. In all cases, when the vacuum vessel pressure suppression system is activated, most of the radioactive inventory is carried to the suppression pool where it remains for the duration of the event. Releases in these events are well within ITER release limits.

Accidents involving the ingress of air, helium, or water into the cryostat of the International Thermonuclear Experimental Reactor (ITER) tokamak design have been analyzed with a modified version of the MELCOR code for the ITER Non-site Specific Safety Report (NSSR-1). The air ingress accident is the result of a postulated breach of the cryostat boundary into an adjoining room. MELCOR results for this accident demonstrate that the condensed air mass and increased heat loads are not a magnet safety concern, but that the partial vacuum in the adjoining room must be accommodated in the building design. The water ingress accident is the result of a postulated magnet arc that results in melting of a Primary Heat Transport System (PHTS) coolant pipe, discharging PHTS water and PHTS water activated corrosion products and HTO into the cryostat. MELCOR results for this accident demonstrate that the condensed water mass and increased heat loads are not a magnet safety concern, that the cryostat pressure remains below design limits, and that the corrosion product and HTO releases are well within the ITER release limits.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008