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Insertion of layers displaying field-induced metal-to-insulator (M/I) transition in ferroelectric tunnel junctions (FTJs) has received attention as a potentially useful way to enlarge junction tunnel electroresistance (TER). Half-doped manganites being at the verge of metal-insulator character are thus good candidates to be slave layers in FTJs. However, the phase diagram of these oxides is extremely sensitive to strain and thus can be radically different when integrated in epitaxial FTJs. Here we report a systematic study of large-area (A = 4 to 100 m2) Pt/La0.5Sr0.5MnO3/BaTiO3/La0.7Sr0.3MnO3 (Pt/HD/BTO/LSMO) FTJs, having different thicknesses of the ferroelectric (2-3nm) and HD layers (1-2nm), grown on substrates imposing either tensile (SrTiO3) or compressive (LaAlO3) strains. Room-temperature electric characterization of the FTJs shows polarization-controlled ON/ OFF states. Clear evidences of field-induced M/I transition (difference between junction resistance in OFF and ON state is increased of more than one order of magnitude) are observed in junctions prepared on SrTiO3 but the HD layer is generally metallic on LaAlO3. Moreover, the M/I transition is only confined in an interfacial layer of the slave film thus entailing an overall reduction of TER. The orderly results reported here give some hints towards selection of HD materials and substrates for optimal FTJ responsiveness., This work has been partially supported by grants from the Spanish Government (MAT2014-56063-C2-1R, MAT2015-73839-JIN and SEV-2015-0496), by the Catalan Government (2014 SGR 734) and by Fondazione Cariplo via the project MAGISTER (grant n. 2013-0726). IF acknowledges Juan de la Cierva – Incorporación postdoctoral fellowship (IJCI-2014-19102).

GeTe has been predicted to be the father compound of a new class of multifunctional materials, ferroelectric Rashba semiconductors, displaying a coupling between spin-dependent k-splitting and ferroelectricity. In this paper, we report on epitaxial Fe/GeTe(111) heterostructures grown by molecular beam epitaxy. Spin-pumping experiments have been performed in a radio-frequency cavity by pumping a spin current from the Fe layer into GeTe at the Fe ferromagnetic resonance and detecting the transverse charge current originated in the slab due to spin-to-charge conversion. Preliminary experiments indicate that a clear spin to charge conversion exists, thus unveiling the potential of GeTe for spin-orbitronics.

Patterning nanoscale protein gradients is crucial for studying a variety of cellular processes in vitro. Despite the recent development in nano-fabrication technology, combining nanometric resolution and fine control of protein concentrations is still an open challenge. Here, we demonstrate the use of thermochemical scanning probe lithography (tc-SPL) for defining micro- and nano-sized patterns with precisely controlled protein concentration. First, tc-SPL is performed by scanning a heatable atomic force microscopy tip on a polymeric substrate, for locally exposing reactive amino groups on the surface, then the substrate is functionalized with streptavidin and laminin proteins. We show, by fluorescence microscopy on the patterned gradients, that it is possible to precisely tune the concentration of the immobilized proteins by varying the patterning parameters during tc-SPL. This paves the way to the use of tc-SPL for defining protein gradients at the nanoscale, to be used as chemical cues e.g. for studying and regulating cellular processes in vitro.

The fine control of the exchange coupling strength and blocking temperature ofexchange bias systems is an important requirement for the development of magnetoresistive sensors with two pinned electrodes. In this paper, we successfully tune these parameters in top- and bottom-pinned systems, comprising 5 nm thick Co40Fe40B20 and 6.5 nm thick Ir22Mn78 films. By inserting Ru impurities at different concentrations in the Ir22Mn78 layer, blocking temperatures ranging from 220 °C to 100 °C and exchange bias fields from 200 Oe to 60 Oe are obtained. This method is then applied to the fabrication of sensors based on magnetic tunneling junctions consisting of a pinned synthetic antiferromagnet reference layer and a top-pinned sensing layer. This work paves the way towards the development of new sensors with finely tuned magnetic anisotropies.

Photoelectron spectroscopy in combination with piezoforce microscopy reveals that the helicity of Rashba bands is coupled to the nonvolatile ferroelectric polarization of GeTe(111). A novel surface Rashba band is found and fingerprints of a bulk Rashba band are identified by comparison with density functional theory calculations.

Genomics is the study of an organism's genome aimed at the functional specification of the different parts of the sequence that comprise the blueprint of the living cell to unveil the mechanisms of the physiology of the cell and its basic, develop- mental, and tissue-specific processes. Proteomics is the comprehensive study of the executive molecules of the cell coded by the genome, further raising the level of complexity, because of the large amplification in the number, going from genes to proteins, and to the sophisticated struc- tural and functional characterization of protein products, which confer specific biochemical properties. While continuous progress in technology provides new experimental solutions to study and measure the behavior of genes and proteins in the cell, the analysis and the management of biological data cannot be uncoupled from the use of mathema- tics, statistics, and informatics disciplines that play a key role in modern molecular biology. together, genomics and proteomics, meant as complementary approaches, delineate the framework of modern molecular medicine, where the knowledge of the functional mechanisms on a subcellular scale, both under physiologic and pathologic conditions, may lead to an improvement in diagnosis, therapy, and drug development.

Thin films of non-evaporable getters are employed in the field of electronic devices packaging, as they provide a simple and effective solution for pumping in sealed applications. In particular thin films of Zr–Co–rare earth alloys deposited by sputtering have been developed for this purpose and successfully employed in industrial applications. In this paper we present an X-ray photoelectron spectroscopy investigation of the effect of thermal activation of the getter from the point of view of the induced surface chemical modification as seen by such a surface sensitive technique. We find that the activation process reflects in a clear reduction of Zr, accompanied by a decrease of the oxygen concentration at surface, which is fully accomplished already at 350 °C; while at 450 °C there is a significant increase of the cobalt concentration at surface.

The surface band bending in ZnSe(0 0 1), as a function of the temperature, is investigated both in the valence band (by photoemission) and in the conduction band (by inverse photoemission and absorbed current spectroscopies). Two different mechanisms are invoked for interpreting the experimental data: the band bending due to surface states, and the surface voltage induced by the incident beam. While the latter is well known in photoemission (surface photovoltage), we demonstrate the existence of a similar effect in inverse photoemission and absorbed current spectroscopies, induced by the incident electrons instead of photons. These results point to the importance of considering the surface voltage effect even in electron-in techniques for a correct evaluation of the band bending.

Epitaxial orthorhombic YMnO3 thin films, (0 0 1) oriented, have been grown by pulsed laser deposition on (0 0 1)SrTiO3 substrates. Their crystal structure and magnetic response have been studied in detail. Although bulk o-YMnO3 is antiferromagnetic, our magnetic measurements reveal intriguing thermal hysteresis between the zero-field-cooled and field-cooled curves below the onset of the antiferromagnetic ordering temperature, thus signaling a more complex magnetic structure with net ferromagnetic moments. We discuss on the possible origin of this net magnetization and we have found a correlation of the magnetic response with the strain state of the films. We propose that substrate-induced strain modifies the subtle competition of magnetic interactions and leads to a non-collinear magnetic state that can thus be tuned by strain engineering.

In analogy with the case of Sr on Si [Y. Liang, S. Gan, M. Engelhard, Appl. Phys. Lett. 79 (2001) 3591], we studied surface crystallinity and oxidation behaviour of clean and Ba terminated Ge(1 0 0) surfaces as a function of oxygen pressure and temperature. The structural and chemical changes in the Ge surface layer were monitored by LEED, XPS and real-time RHEED. In contrast to the oxidation retarding effect, observed for 1/2 monolayer of Sr on Si, the presence of a Ba termination layer leads to a pronounced increase in Ge oxidation rate with respect to clean Ge. In fact, while the Ge(1 0 0) surface terminated with 1/2 ML Ba amorphizes for a p O 2 of 10 −2 Torr, LEED indicates that clean Ge forms a thin (4.5 A), 1 × 1 ordered oxide upon aggressive O 2 exposure (150 Torr, 200 °C, 30 min). We briefly discuss the origins for the difference in behaviour between Ba on Ge and Sr on Si.

The ferroelectric polarization and short-circuit photocurrent in BaTiO3 thin films have been studied for different contact configurations that allow to measure the photoresponse and polarization under the presence of large or negligible imprint field. It is found that in all cases, the direction of the photocurrent is dictated by the depolarizing field and ultimately by the film polarization, with a negligible contribution of the imprint electric field. However, dramatic differences are found in their time-dependent photoresponse. Whereas in presence of imprint, steady photocurrents are observed under suitable illumination, transient photocurrents are generated in absence of imprint. It is argued that this distinct behavior is determined by the different Schottky barrier height at electrodes which thus offers a simple way to tune the film photoresponse. These findings could be exploited for electro-optic read-out and writing of ferroelectric memories.

In-vitro tests and analyses are of fundamental importance for investigating biological mechanisms in cells and bio-molecules. The controlled application of forces to activate specific bio-pathways and investigate their effects, mimicking the role of the cellular environment, is becoming a prominent approach in this field. In this work, we present a non-invasive magnetic on-chip platform which allows for the manipulation of magnetic particles, through micrometric magnetic conduits of Permalloy patterned on-chip. We show, from simulations and experiments, that this technology permits to exert a finely controlled force on magnetic beads along the chip surface. This force can be tuned from few to hundreds pN by applying a variable external magnetic field.

We used Pulsed Laser Deposition (PLD) in oxidizing environment to epitaxially grow optimally doped manganite La2 / 3Sr1 / 3MnO3 (LSMO) thin films over a (001) oriented SrTiO3 substrate. Synthesized samples show good room temperature magnetic properties accompanied by a peculiar extension of the metallic conduction regime to temperatures higher than the Curie point. In this paper we present a study of the dependence of transport and magnetic properties of LSMO thin films on the oxygen pressure during PLD growth. We show how interaction of the growing films with O2 molecules is fundamental for a correct synthesis and in which way it is possible to adjust PLD experimental parameters in order to tune LSMO thin film properties. The persistence of the metallic conduction regime above the Curie temperature indicates some minor changes of the electronic structure near the Fermi level, which is responsible for the half-metallic behavior of LSMO at low temperature. This feature is rather intriguing from the technological point of view, as it could pave the way to the increase of operating temperature of devices based on LSMO.

During the deposition process of high-k gate oxides on Ge, the Ge interface tends to be oxidized to form GeOx, leading to the introduction of interface states which compromise transistor performance. It has been suggested that a Ba termination layer on Ge could fulfill the same passivating role on Ge as reported for Sr on Si. In this paper, we present LEED, UPS and XPS studies on the effect of Ba overlayers on the chemical and electrical passivation of Ge(1 0 0). For 1 ML coverage, the adsorbate phase has (1×1) symmetry, as observed by LEED. Ba is seen to significantly increase the oxidation tendency of the Ge(1 0 0) surface. Using UPS, 1 ML Ba was seen to reduce surface band bending by 200 meV on n-type Ge, suggesting that Ba deposition causes transfer of electrons to the Ge substrate, resulting in a surface dipole. The role of this dipole in oxidation enhancement and possible electronic passivation effects is discussed.

This work addresses the issue of the quality of La 0.7 Sr 0.3 MnO 3 (LSMO) surfaces integrated in tunnelling junctions. From a detailed X-ray photoemission spectroscopy analysis it results that Sr segregates at the surface of LSMO films grown by pulsed laser deposition at high O 2 pressure (350 mTorr). This fact is attributed to the presence of an outermost SrO layer, which is critical for the subsequent formation of a good LSMO/insulator interface. In particular we found that the unique properties of the junctions employing SrTiO 3 as insulator, are strictly correlated to the integration of the SrO segregated layer in the SrTiO 3 structure.

We describe the construction and operation of an ultrahigh-vacuum system devoted to the study of thin film magnetism. The apparatus includes a growth chamber, where ultrathin films are deposited by molecular beam epitaxy, and a measurement chamber, where they are analyzed by a variety of electron spectroscopies. The electron spin can be controlled by using a fully characterized spin resolved electron gun and polarization analyzers. Test measurements on in situ grown Fe/MgO(001) samples are also presented as illustration of the system performances.

The magneto-ionic effect is a promising method to control the magnetic properties electrically. Charged mobile oxygen ions can easily be driven by an electric field to modify the magnetic anisotropy of a ferromagnetic layer in contact with an ionic conductor in a solid-state device. In this paper, we report on the room temperature magneto-ionic modulation of the magnetic anisotropy of ultrathin CoFeB films in contact with a GdOx layer, as probed by polar micro-Magneto Optical Kerr Effect during the application of a voltage across patterned capacitors. Both Pt/CoFeB/GdOx films with perpendicular magnetic anisotropy and Ta/CoFeB/GdOx films with uniaxial in-plane magnetic anisotropy in the as-grown state exhibit a sizable dependence of the magnetic anisotropy on the voltage (amplitude, polarity, and time) applied across the oxide. In Pt/CoFeB/GdOx multilayers, it is possible to reorient the magnetic anisotropy from perpendicular-to-plane to in-plane, with a variation of the magnetic anisotropy energy greater...

Ge-based spin-photodiodes have been employed to investigate the spectral dependence of optical spin orientation in germanium, in the range 400--1550 nm. We found the expected maximum in the spin polarization of photocarriers for excitation at the direct gap in $\ensuremath{\Gamma}$ (1550 nm) and a second sizable peak due to photogeneration in the $L$ valleys (530 nm). Data suggest distinct spin depolarization mechanisms for excitation at $\ensuremath{\Gamma}$ and $L$, with shorter spin relaxation times whether the $X$ point is involved. These devices can be used as integrated photon-helicity detectors over a wide spectral range.

Recent studies have demonstrated the potential of antiferromagnets as the active component in spintronic devices. This is in contrast to their current passive role as pinning layers in hard disk read heads and magnetic memories. Here we report the epitaxial growth of a new high-temperature antiferromagnetic material, tetragonal CuMnAs, which exhibits excellent crystal quality, chemical order and compatibility with existing semiconductor technologies. We demonstrate its growth on the III-V semiconductors GaAs and GaP, and show that the structure is also lattice matched to Si. Neutron diffraction shows collinear antiferromagnetic order with a high Ne\'el temperature. Combined with our demonstration of room-temperature exchange coupling in a CuMnAs/Fe bilayer, we conclude that tetragonal CuMnAs films are suitable candidate materials for antiferromagnetic spintronics., Comment: 16 pages, 5 figures, Published in Nature Communications (2013)

The magnetotransport phase diagram of half-doped manganites ${\text{Ln}}_{0.5}{\text{A}}_{0.5}{\text{MnO}}_{3}$ ($\text{Ln}={\text{La}}^{3+}$, ${\text{Nd}}^{3+}$, etc., and $\text{A}={\text{Sr}}^{2+}$, ${\text{Ca}}^{2+}$, etc.) is primarily dictated by the bare conduction bandwith (${W}_{0}$), which itself is controlled by the Mn-O-Mn bond angle, and the carrier concentration. In thin films, epitaxial strain (\ensuremath{\epsilon}) provides an additional tool to tune ${W}_{0}$ by selecting orbital ordering at fixed carrier concentration. Here, we will show that compressive or tensile epitaxial strain on half-doped manganites can have a tremendous and distinct effect on ${\text{La}}_{0.5}{\text{Sr}}_{0.5}{\text{MnO}}_{3}$ (LSMO5) and ${\text{La}}_{0.5}{\text{Ca}}_{0.5}{\text{MnO}}_{3}$ (LCMO5), having broad or narrow ${W}_{0}$, respectively. It is found that in LSMO5, large compressive strain triggers a change from a ferromagnetic and metallic ground state to an insulating and antiferromagnetic state whereas a tensile strain produces an antiferromagnetic but metallic state. In contrast, under strain, LCMO5 remains an antiferromagnetic insulator irrespectively of the strain state. These results illustrate that orbital ordering largely depends on the interplay between ${W}_{0}$ and \ensuremath{\epsilon} and provide a guideline towards responsive manganite layers.

We present the design and the preliminary experimental characterization of a novel lab-on-a-chip platform for high-sensitivity impedimetric detection of single magnetic beads employed as magnetic cargos with molecular payload for accurate drug delivery. The real-time impedimetric detection of these superparamagnetic microbeads in saline solution is here experimentally demonstrated (20 nS conductance variation for a single 1μm bead), validating the insulating-sphere model and the finite-element simulations employed for optimal electrode design. A custom electronic front-end for impedance tracking in the 1-10 MHz range, required to compensate the impact of the large parasitic impedance due to the silicon substrate, is also presented. Thanks to introduction of an ad-hoc noise cancelling network based on a dummy circuit and a phase shifter for low-frequency phase noise counteraction by active subtraction, slow fluctuations are significantly reduced (by a factor 10), allowing a SNR > 10.

In this paper we present an innovative on-chip platform suitable for the simultaneous manipulation and detection of the transit of a single magnetic bead. This system is based on the controlled displacement of constrained magnetic domain walls (DWs) that are used to move and sense particles in suspension over the chip. To this scope, the high stray field from the transverse DWs created at the corners of ferromagnetic zig-zag structures is used for particles manipulation, while electrical contacts flanking a single corner are employed to simultaneously monitor the DW passage through that corner, via anisotropic magneto resistance (AMR) measurements. A single DW carrying a magnetic particle is nucleated and manipulated within the zig-zag shaped magnetic conduit, trough the action of external magnetic fields. At the same time, the variation of the voltage drop across a corner flanked by a pair of electrical leads is measured, allowing to detect the transit of the DW thanks to the change of the relative orientation of current and spins at the corner related to the peculiar micromagnetic configuration of the DW (AMR). Work is in progress in order to selectively distinguish the transit of a naked DW from that of a DW bound to a magnetic particle. This work paves the way to the development of a closed-loop microlfuidic platform for on-chip bead manipulation, where single bead can be finely moved and their motion continuously checked, via AMR electrical detection and without need of optical monitoring, in a fully integrated closed-loop system.

We report on the measurements of spin diffusion length and lifetime in Germanium with both magneto-electro-optical and magneto-electrical techniques. Magneto-electro-optical measurements were made by optically inject in Fe/MgO/Ge spin-photodiodes a spin polarized population around the Γ point of the Brillouin zone of Ge at different photon energies. The spin diffusion length is obtained by fitting by a mathematical model the photon energy dependence of the spin signal, due to switching of the light polarization from left to right, leading to a spin diffusion length of 0.9±0.2 μm at room temperature. Non-local four-terminals and Hanle measurements performed on Fe/MgO/Ge lateral devices, at room temperature, instead lead to 1.2±0.2 μm. The compatibility of these values among the different measurement methods validates the use all of all of them to determine the spin diffusion length in semiconductors. While electrical methods are well known in semiconductor spintronics, in this work we demonstrate that the optical pumping versus photon energy is an alternative and reliable method for the determination of the spin diffusion length whereas the band structure of the semiconductor allows for a non-negligible optical spin orientation.

International audience; We investigate by broadband femtosecond pump-probe spectroscopy the transient optical response of a metal-dielectric Bragg filter (MDBF) made of thin layers of gold and fused silica. A quantitative comparison of the experimental results with a semiclassical model with no fitting parameters allows us to disentangle all the different contributions to the transient optical response of the MDBF, which include the ultrafast dynamics of thermalized and nonthermalized electrons as well as of lattice phonons excited in the metal layers. Furthermore, we provide a quantitative comparison of the optical response of the MDBF with that of a single gold layer under comparable excitation conditions. The results clearly show the advantages and disadvantages of the multilayer configuration in terms of all-optical-modulation capability.

Interfacial magnetoelectric coupling is a viable path to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO3 system, only tiny changes of the interfacial Fe magnetic moment upon reversal of the BaTiO3 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/BaTiO3 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 BaTiO3 polarization. The suppression/recovery of interfacial ferromagnetism results from the asymmetric effect that ionic displacements in BaTiO3 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.

The Fe/BaTiO3 interface is a prototypical artificial multiferroic system displaying purely electronic magnetoelectric effects at room temperature. As magneto-electric coupling is essentially localized at the interface, the properties of the very first Fe layers in contact with BaTiO3 play a major role. In this paper, we investigate, by using X-ray photoemission spectroscopy and photoelectron diffraction, the in-situ growth, by molecular beam epitaxy, of ultrathin Fe films (∼7 monolayers) on a BaTiO3/SrTiO3(001) template. We found that growing the Fe films above room temperature (373 K) is essential in order to avoid island growth and obtain a continuous film. Post-annealing up to 473 K improves the film crystallinity but prevents chemical interdiffusion and roughening. Just an interfacial monolayer of oxidized iron is detected in these conditions, which appears as an unavoidable consequence of the Fe/BaTiO3 chemical interaction. Its active role in magnetoelectric coupling must be carefully taken into account to correlate theoretical predictions and experiments.

We report on the possibility of controlling the maximum demagnetization induced by a femtosecond laser pulse in a CoFeB-based magnetic tunnel junction, by tuning the external bias applied to the junction. We explain this effect in terms of laser-induced spin-polarized currents which can be controlled by tuning the conductivity of the junction. This demonstrates the contribution of spin-polarized currents for laser-induced demagnetization and may pave the way to increase the speed of spintronic devices, using ultrashort laser pulses.

We present a spin resolved inverse photoemission study of Cr ultrathin films (up to few monolayers [ML]) grown on Ag(001) and Fe(001) at room temperature. The magnetic properties of the films are strongly influenced by the different interaction with the substrates. For the Cr/Ag(001) system, where the chemical interaction of the overlayer with the substrate is very small, no polarization dependence of the Cr features is observed, a finding which can fit within the predicted antiferromagnetism of a Cr layer. For the case of Cr/Fe(001), the Cr contribution is strongly polarized in the early stages of the interface formation (up to 2 ML) and then becomes gradually unpolarized.

We present a combined study of structural and electronic properties of thin Co films (up to 50 ML) grown on Fe(001). By means of primary-beam diffraction modulated electron emission, we found a structural transition between a strained bce structure (bct) and the stable hcp phase occurring at similar to 15 ML Co coverage. This structural change has a counterpart in the unoccupied electron states of the Co overlayer, as seen by absorbed current spectroscopy. We demonstrate that the evolution of AC spectra can be used to monitor the mentioned transition and apply this technique to the case of Co grown on Fe(001)-p(1 x 1)O. It is found that the presence of the oxygen causes a delayed onset of the bct-hcp transition.

Oxygen adsorption in an ordered $p(1\ifmmode\times\else\texttimes\fi{}1)$ fashion on the Fe(001) surface has been studied by empty states spectroscopies using a spin-polarized electron beam. The low-energy electron absorption and reflection display a much larger spin dependence in Fe(001)-$p(1\ifmmode\times\else\texttimes\fi{}1)\mathrm{O}$ than in Fe(001). Peak values of the spin asymmetries of the absorbed (reflected) current larger than 13% (45%) at around 9--11 eV above the Fermi level are found. Spin-resolved inverse photoemission reveals that in the same energy range the exchange splitting between majority- and minority-spin states in Fe(001)-$p(1\ifmmode\times\else\texttimes\fi{}1)\mathrm{O}$ is $\ensuremath{\sim}50%$ larger than in the clean surface.

High quality single crystal Fe films to be used in spin polarized electron spectroscopy have been prepared in ultra-high vacuum by epitaxial growth on MgO(001) substrates. Oxygen absorption on the clean surface followed by annealing at 600°C produces a well-ordered p (1×1) overlayer. The low energy electron absorption and reflection from the Fe(001)- p (1×1)O surface display a huge dependence on the polarization of the primary beam. Peak values of the spin asymmetries of the absorbed (reflected) current larger than 13% (45%) around 4–8 eV electron kinetic energy are obtained. The presence of the surface oxide protects the system against contamination, so that an almost negligible asymmetry deterioration is observed after prolonged operation in vacuum. The results are discussed in view of applications in electron spin polarimetry.

Fe films have been prepared in ultrahigh vacuum by epitaxial growth on MgO(001) substrates. Spin-resolved inverse photoemission measurements indicate that nonannealed overlayers display lower spectroscopic quality than the corresponding bulk system. Low energy electron diffraction and x-ray photoemission reveal that annealing promotes oxygen surface segregation giving rise to a c(2×2) reconstruction even in several hundred A thick films. It is found that high-quality Fe(001) single crystal films with clean and well ordered surfaces can be obtained after high temperature annealing (∼600 °C) of relatively thick films (>1000 A).

International audience; Organic semiconductors constitute promising candidates toward large-scale electronic circuits that are entirely spintronics-driven. Toward this goal, tunneling magnetoresistance values above 300% at low temperature suggested the presence of highly spin-polarized device interfaces. However, such spinterfaces have not been observed directly, let alone at room temperature. Thanks to experiments and theory on the model spinterface between phthalocyanine molecules and a Co single crystal surface, we clearly evidence a highly efficient spinterface. Spin-polarised direct and inverse photoemission experiments reveal a high degree of spin polarisation at room temperature at this interface. We measured a magnetic moment on the molecule's nitrogen p orbitals, which substantiates an ab-initio theoretical description of highly spin-polarised charge conduction across the interface due to differing spinterface formation mechanisms in each spin channel. We propose, through this example, a recipe to engineer simple organic-inorganic interfaces with remarkable spintronic properties that can endure well above room temperature

Relativistic effects are increasingly seen as key ingredients in the burgeoning field of spintronics. Among them, the Rashba effect, in which the spin degeneracy is removed as a consequence of spin-orbit interaction in noncentrosymmetric structures, plays a leading role. While the Rashba effect is com- monly associated to two dimensional systems and interfaces, recent reports suggest that a sizeable Rashba splitting might also occur in bulk materials, such as BiTeI. Here we establish, for the first time, a link between Rashba physics and the field of ferroelectricity in single-phase materials, by predicting from first-principles a giant Rashba effect in bulk GeTe, a narrow gap ferroelectric semiconductor. We focus on the dependence of the spin splitting amplitude on the ferroelectric polarization, which makes the spin polarization of the current flowing in GeTe to be controllable and switchable by an electric field. In particular, we demonstrate that a full reversal of the spin polarization, i.e., of the Rashba parameter, can be achieved upon reversal of the ferroelectric polarization. Noteworthy, the hysteretic nature of ferroelectricity provides a unique way to exploit the Rashba effect in novel spintronics devices with non volatile logic func- tions associated with the remanent ferroelectric states. As an example, the design of a spin FET employing a bulk GeTe channel is discussed.

In this work, calculations and preliminary experimental data for determining the optimal condition for the selective bio-functionalization of magnetic tunneling junction (MTJ)-based biosensors are presented. Results on the detection of biomolecular recognition events employing MTJ-based sensor and magnetic beads are presented and interpreted through calculations, taking into account the dependence of the signal on the distribution of the beads with respect to the sensor. Furthermore, it is demonstrated by calculations that a significant increase in the sensor sensitivity and quantification capability can be achieved by selectively bio-functionalizing an area which corresponds to the sensor active area.

Electric Control of the Giant Rashba Effect in Bulk GeTe Domenico Di Sante, Paolo Barone, Riccardo Bertacco and Silvia Picozzi* Adv. Mater. 2013, 25, 509–513 DOI: 10.1002/adma.201203199 The following errors appeared in the above-mentioned article: k-vector values have to be multiplied by a factor of 2π. In turn, effective masses, Rashba parameters as well as the channel length are affected. In the evaluation of the effective masses an additional correction by a factor of 10 must be taken into account. Specifi cally, we report in the Table below the values that have to be corrected.

A commonly used figure of merit of magnetoresistive sensors employed to detect magnetic beads labeling biomolecules in lab-on-chip applications is the sensor sensitivity (So) to external magnetic fields in the linear region of the sensor. In this paper we show that, in case of lock-in detection and bead excitation by a small AC magnetic field, S-0 is not the good figure of merit to optimize. Indeed, the highest sensitivity to the magnetic beads is achieved biasing the sensor in the region of its characteristics where the product between the DC bias field and the second derivative of the resistance with respect to the magnetic field is maximum. The validity of this criterion, derived from a phenomenological model of bead detection, is proved in case of magnetic tunneling junction sensors detecting magnetic beads with 250 nm diameter. This work paves the way to the development of a new generation of sensors properly designed to maximize the bead sensitivity. (C) 2013 Elsevier B.V. All rights reserved.

The measurement of the spin diffusion length and/or lifetime in semiconductors is a key issue for the realisation of spintronic devices, exploiting the spin degree of freedom of carriers for storing and manipulating information. In this paper, we address such parameters in germanium (0 0 1) at room temperature (RT) by three different measurement methods. Exploiting optical spin orientation in the semiconductor and spin filtering across an insulating MgO barrier, the dependence of the resistivity on the spin of photo-excited carriers in Fe/MgO/Ge spin photodiodes (spin-PDs) was electrically detected. A spin diffusion length of 0.9 ± 0.2 µm was obtained by fitting the photon energy dependence of the spin signal by a mathematical model. Electrical techniques, comprising non-local four-terminal and Hanle measurements performed on CoFeB/MgO/Ge lateral devices, led to spin diffusion lengths of 1.3 ± 0.2 µm and 1.3 ± 0.08 µm, respectively. Despite minor differences due to experimental details, the order of magnitude of the spin diffusion length is the same for the three techniques. Although standard electrical methods are the most employed in semiconductor spintronics for spin diffusion length measurements, here we demonstrate optical spin orientation as a viable alternative for the determination of the spin diffusion length in semiconductors allowing for optical spin orientation.

We report the results of a combined UV photoemission and inverse photoemission spectroscopy investigation of some isostructural rare earth (R) intermetallic compounds, i.e. CeCo 2 , LuCo 2 , CeRh 2 , LuRh 2 , Ce 7 Rh 3 and Lu 7 Rh 3 , aiming to highlight the effects, on both the occupied and unoccupied d-derived partial density of states, of R substitution on different transition metal (M) hosts. These effects cannot be detected by X-ray spectroscopies because of the sizeable f-related contribution while, for cross-section reasons, UV spectroscopies may allow direct access to the d-like states. The results are discussed in terms of the different spatial extents of Ce and Lu 5d wavefunctions and of the degree of intermixing with the M partner d valence states.

We report on spin-photodiodes based on fully epitaxial Fe/MgO/Ge(001) heterostructures for room temperature integrated detection of light helicity at 1300 nm and 1550 nm wavelengths. The degree of circular polarization of light determines the spin direction of photo-carriers in Ge that are filtered by the Fe/MgO analyzer. Spin-detection experiments are performed by measuring the photocurrent while illuminating the spin-photodiodes with left or right circularly polarized light, under the application of a magnetic field parallel to the light direction which drives the Fe magnetization out of plane. We found that the spin-photodiodes spin filtering asymmetry is reduced by ∼40% in forward bias and by less than 15% in reverse bias, when increasing the photon wavelength from 1300 nm to 1550 nm. This result, apparently counterintuitive because of the larger spin polarization of the photo-carriers generated at 1550 nm with respect to that at 1300 nm, is explained in terms of the different spatial profile of carrier generation inside Ge. The larger penetration depth of light at 1550 nm leads to a smaller polarization of photocarriers when they reach the MgO tunneling barrier, due to the more efficient spin relaxation during transport.

The remote manipulation of micro and nano-sized magnetic particles carrying molecules or biological entities over a chip surface is of paramount importance for future on-chip applications in biology and medicine. In this paper, we present a method for the on-chip demultiplexing of individual magnetic particles using bifurcated magnetic nano-conduits for the propagation of constrained domain walls (DWs). We demonstrate that the controlled injection and propagation of a domain wall in a bifurcation allow capturing, transporting, and sorting a single magnetic particle between two predefined paths. The cascade of n levels of such building blocks allows for the implementation of a variety of complex sorting devices as, e.g., a demultiplexer for the controlled sorting among 2n paths.

The authors thank J. Gazquez and M. Varela for the transmission electron microscopy analysis, and G. Isella, P. Vavassori, H. Jaffres, and A. Fert for fruitful discussions. N.M.C. and S. S. thank Ivan Rungger for making available a version of Smeagol dealing with electrodes made of different materials, and for useful discussions. This work was partially supported by Science Foundation Ireland (Grant No. 07/IN.1/I945). The Smeagol code was supported by CRANN and by KAUST (ACRAB project).

The effect of the proximity of Au on the electronic and magnetic properties of La 0.66 Sr 0.33 MnO 3 (LSMO) has been investigated by means of ab initio calculations within the density-functional theory. The calculations show an orbital reconstruction of the interfacial Mn, which is due more to the presence of a discontinuity rather than to a real chemical interaction with Au atoms. In fact, the same orbital reconstruction is found in the free LSMO surface. In both cases of Au/LSMO and LSMO surface, the Mn magnetic moments change very little with respect to the bulk case. In general, the calculations show a negligible influence of the Au atomic layer on LSMO at an ideal interface, with the LSMO surface magnetic and electronic properties essentially unchanged.

We have grown an ultrathin epitaxial Fe/MgO bilayer on (Ga, Mn)As by e-beam evaporation in UHV. The system structure has been investigated by high resolution transmission electron microscopy (TEM) experiments which show that the Fe and MgO films, covering completely the (Ga, Mn) As, grow with the epitaxial relationship Fe[100](001) parallel to begin_of_the_skype_highlighting (001) parallel to FREE end_of_the_skype_highlighting MgO[110](001) parallel to (Ga, Mn)As[110](001). The magnetic reversal process, studied by the magneto-optical Kerr effect (MOKE) at room temperature, demonstrates that the iron is ferromagnetic and possesses a cubic anisotropy, confirming the epitaxy relationship found with TEM. Resistivity measurements across the barrier display a non-Ohmic behavior characterized by cubic conductance as a function of the applied voltage suggesting tunneling-dominated transport across the barrier.

We report on spin-photodiodes based on fully epitaxial Fe/MgO/Ge(001) heterostructures for the room temperature integrated detection of light helicity at a wavelength of 1300 nm. The degree of circular polarization of light is related to the spin direction of photo-excited carriers in Ge that are filtered by the MgO barrier, with probabilities differing for the two spin channels. Spin-detection experiments are performed by illuminating spin-photodiodes using left or right circularly polarized light under the application of a magnetic field parallel to the light direction and measuring the current crossing the device. We found that the maximum percentage variation of the photocurrent due to full reversal of the light helicity is on the order of 5.9% at room temperature. This variation can be attributed in part to the magnetic circular dichroism of Fe (0.8%) but mainly to the spin filtering of photo-generated carriers across the MgO barrier.