1,721,045 research outputs found
Magnetic Tunneling Junctions for biosensors: From the growth to the detection
Full text linkIn the last ten years, magnetoelectronics has emerged as a promising new platform technology for biosensor and biochip development. In particular, magnetoresistive-based sensors, conventionally used as read heads in hard disk drives, have been used in combination with biologically functionalized magnetic labels to demonstrate the detection of molecular recognition. In this paper, the growth and fabrication of spintronic transducers based on the magnetoresistance of tunneling magnetic junctions are described. Moreover the detection of 250 nm streptavidin magnetic beads is presented
Domain wall engineering through exchange bias
Full text linkThe control of the structure and position of magnetic domain walls is at the basis of the development of different magnetic devices and architectures. Several nanofabrication techniques have been proposed to geometrically confine and shape domain wall structures; however, a fine tuning of the position and micromagnetic configuration is hardly achieved, especially in continuous films. This work shows that, by controlling the unidirectional anisotropy of a continuous ferromagnetic film through exchange bias, domainwalls whose spin arrangement is generally not favored by dipolar and exchange interactions can be created. Micromagnetic simulations reveal that the domain wall width, position and profile can be tuned by establishing an abrupt change in the direction and magnitude of the exchange bias field set in the system
Structural comparison between MgO/Fe(0 0 1) and MgO/Fe(0 0 1)-p(1 × 1)O interfaces for magnetic tunneling junctions: An Auger electron diffraction study
No full textActivation of Zr-Co-rare earth getter films: An XPS study
No full textThin 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
Electric field control of magnetic anisotropies and magnetic coercivity in Fe/BaTiO3 (001) heterostructures
No full textElectric field control of magnetic anisotropies and magnetic coercivity in Fe/BaTiO3 (001) heterostructure
Epitaxial growth of Fe/MgO/Ge(001) heterostructures
No full textWe report on the growth of epitaxial Fe/MgO heterostructures on Ge(0 0 1) by Molecular Beam Epitaxy. The better crystal quality and interfacial chemical sharpness at the oxide–semiconductor interface have been obtained by growing MgO at room temperature, followed by a post-annealing at 773 K, on top of a p(2 1)-Ge(0 0 1) clean surface. The growth of Fe at room temperature followed by annealing at 473 K gives the best epitaxial structure with optimized crystallinity of each layer compatible with limited chemical interdiffusion. Tunneling devices based on the epitaxial Fe/MgO/Ge heterostructure have been micro-fabricated and tested in order to probe the electrical properties of the MgO barrier. The current–voltage characteristics clearly show that tunneling is the dominant phenomenon, thus indicating that this system is very promising for practical applications in electronics and spintronics
Bandstructure line-up of epitaxial Fe/MgO/Ge heterostructures: A combined x-ray photoemission spectroscopy and transport study
No full textThe bandstructure line-up of Fe/MgO/Ge heterostructures with various Ge doping has been determined by x-ray photoemission spectroscopy. The MgO layer causes a sizable depinning of the Fermi level in Ge for light n-1015 cm−3 and moderate p-doping 1018 cm−3, but not for heavy n-doping 1020 cm−3. The Fermi level instead stays essentially in the middle of the MgO gap for all the investigated doping. This picture agrees with transport measurements only for moderate n- or p-doping, while we demonstrate that for heavy n-doping the analysis of the conductance versus temperature fails in predicting the Schottky barrier height
Near-room-temperature control of magnetization in field effect devices based on La0.67Sr0.33MnO3 thin films
No full textThe control of the magnetization in ferromagnetic layers via electric fields is a hot topic in view of applications to the next generation of spintronic devices, where writing the magnetic information through current lines could be replaced by electric writing. Mixed valence manganites are good candidates for such a purpose because they present an intriguing coupling between ferromagnetism and charge ordering/doping which can be tuned by the application of an electric field. Here we present results on the near-room temperature control of the magnetization of optimally doped La0.67Sr0.33MnO3 ultrathin films in vertical field effect devices, where they act as top or bottom electrodes. In the latter case a slight decrease in the Curie temperature 5 K is observed after application of 5107 V/m, i.e., the maximum field preventing electric breakdown, compatible with the induced variation in the charge density and mixed valence within the Thomas Fermi screening length. These results indicate that electric fields achievable in vertical field effect devices, of the same entity of interfacial fields originating from differences in the work function in heterostructures, have only minor influence on the magnetic properties of optimally doped ultrathin
La0.67Sr0.33MnO3 films
Epitaxial Fe/MgO/Ge spin-photodiodes for integrated detecion of light helicity at room temperature
No full textWe 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
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