Suchergebnisse

ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License. ; The successful application of focused electron (and ion) beam induced deposition techniques for the growth of nanowires on flexible and transparent polycarbonate films is reported here. After minimization of charging effects in the substrate, sub-100 nm-wide Pt, W, and Co nanowires have been grown and their electrical conduction is similar compared to the use of standard Si-based substrates. Experiments where the substrate is bent in a controlled way indicate that the electrical conduction is stable up to high bending angles, >50°, for low-resistivity Pt nanowires grown by the ion beam. On the other hand, the resistance of Pt nanowires grown by the electron beam changes significantly and reversibly with the bending angle. Aided by the substrate transparency, a diffraction grating in transmission mode has been built based on the growth of an array of Pt nanowires that shows sharp diffraction spots. The set of results supports the large potential of focused beam deposition as a high-resolution nanolithography technique on transparent and flexible substrates. The most promising applications are expected in flexible nano-optics and nanoplasmonics, flexible electronics, and nanosensing. ; This work was supported by Spanish Ministry of Economy and Competitivity through projects No. MAT2011-27553-C02 and MAT2014-51982-C2-1-R including FEDER funds and by the Aragon Regional Government. ; Peer Reviewed

In this work, we present a detailed investigation of the magnetic properties of cobalt nanospheres grown on cantilever tips by focused electron beam induced deposition (FEBID). The cantilevers are extremely soft and the cobalt nanospheres are optimized for magnetic resonance force microscopy (MRFM) experiments, which implies that the cobalt nanospheres must be as small as possible while bearing high saturation magnetization. It was found that the cobalt content and the corresponding saturation magnetization of the nanospheres decrease for nanosphere diameters less than 300 nm. Electron holography measurements show the formation of a magnetic vortex state in remanence, which nicely agrees with magnetic hysteresis loops performed by local magnetometry showing negligible remanent magnetization. As investigated by local magnetometry, optimal behavior for high-resolution MRFM has been found for cobalt nanospheres with a diameter of ≈200 nm, which present atomic cobalt content of ≈83 atom % and saturation magnetization of 106 A/m, around 70% of the bulk value. These results represent the first comprehensive investigation of the magnetic properties of cobalt nanospheres grown by FEBID for application in MRFM. ; This work was supported by Spanish Ministry of Economy and Competitivity through projects No. MAT2014-51982-C2-1-R, MAT2014-51982-C2-2-R and MAT2015-69725-REDT (including FEDER funds), by the Aragon Regional Government, and by EU (Cost Action CM1301- CELINA and ESTEEM2 projects). ; Peer reviewed

Under the terms of the Creative Commons Attribution 3.0 Unported License to their work. ; We show here that using spin orbit coupling interactions at a metallic interface it is possible to control the sign of the spin to charge conversion in a spin pumping experiment. Using the intrinsic symmetry of the "Inverse Rashba Edelstein Effect" (IREE) in a Bi/Ag interface, the charge current changes sign when reversing the order of the Ag and Bi stacking. This confirms the IREE nature of the conversion of spin into charge in these interfaces and opens the way to tailoring the spin sensing voltage by an appropriate trilayer sequence. ; We would like to acknowledge financial support from the European Commission through the Marie Curie Intra European Fellowship Project No. 301656: AtomicFMR, funded by the 7th Framework Programme. This work was supported by Spanish Ministry of Economy and Competitivity through Project No. MAT2011-27553-C02, including FEDER funds, and by the Aragon Regional Government. ; Peer reviewed

5 pages, 5 figures.-- PACS nrs.: 75.47.-m; 73.50.Jt; 75.50.Bb.-- ©2009 The American Physical Society. ; We report Hall-effect measurements of epitaxial Fe (001) thin films grown on MgO (001). We have focused on the dependence of the anomalous Hall effect (AHE) in heteroepitaxial structures MgO (001)//Fe(t)/MgO with t=10, 2.5, 2, 1.8, and 1.3 nm. Our results have been interpreted in terms of a recent unified theory of the AHE. We have demonstrated that the thickness and roughness of the Fe layer are control parameters to tune both the longitudinal conductivity σ(xx) and anomalous Hall conductivity σ(xy). In this way, we report a crossover from the intrinsic moderately dirty region of conductivities where σ(xy) = const to the dirty region of poorly conducting materials (σ(xx) < 10^4 S/cm) where we have found that the relation σ(xy) proportional to σ(xx)^n with n = 1.66(4) holds, in good agreement, with the expected universal scaling relationship reported in other ferromagnetic compounds. ; Financial support by the Spanish Ministry of Science (MEC) through Projects No. MAT2005-05565-C02 and No. MAT2008-06567-C02 including FEDER funding, and the Aragon Regional Government (Group E26) are acknowledged. ; Peer reviewed

6 páginas, 8 figuras, 1 tabla.-- PACS number(s): 73.20.-r, 73.25.+i, 73.50.Jt ; We have investigated the magnetotransport properties of ultrathin films of Bi grown on thermally oxidized Si(001) substrates with thickness ranging from 10 to 100 nm at temperatures down to 2 K and in magnetic fields up to 90 kOe. Remarkable differences both in temperature and field dependence of the Hall resistivity are found for the films with thickness above and below 20 nm. These observations can be explained due to the presence of surface states, which play an important role in determining the electronic transport properties of the thinnest films. The estimated surface carrier density 4×1013 cm−2 at room temperature correlates well with that recently reported from angle-resolved photoemission spectroscopy on ultrathin Bi(001) films. ; This work was supported by Spanish Ministry of Science (through Projects No. MAT2007-65965-C02-02 and No. MAT2008-06567-C02) including FEDER funding, the Aragón Regional Government and the Universidad Complutense de Madrid. N.M. and S.S. acknowledge financial support from Spanish CSIC (JAE program) and Spanish MEC (FPU program). M.P. acknowledges Comunidad de Madrid and European Social Fund for financial support. ; Peer reviewed

We report on a nanomechanical engineering method to monitor matter growth in real time via e-beam electromechanical coupling. This method relies on the exceptional mass sensing capabilities of nanomechanical resonators. Focused electron beam-induced deposition (FEBID) is employed to selectively grow platinum particles at the free end of singly clamped nanotube cantilevers. The electron beam has two functions: it allows both to grow material on the nanotube and to track in real time the deposited mass by probing the noise-driven mechanical resonance of the nanotube. On the one hand, this detection method is highly effective as it can resolve mass deposition with a resolution in the zeptogram range; on the other hand, this method is simple to use and readily available to a wide range of potential users because it can be operated in existing commercial FEBID systems without making any modification. The presented method allows one to engineer hybrid nanomechanical resonators with precisely tailored functionalities. It also appears as a new tool for studying the growth dynamics of ultrathin nanostructures, opening new opportunities for investigating so far out-of-reach physics of FEBID and related methods. ; This work is supported by the ERC advanced Grant 692876, ERC PoC Grant 862149, the Foundation Cellex, the CERCA Programme, AGAUR, Severo Ochoa (SEV-2015−0522), the Grants FIS2015-69831-P, RTI2018-097953-B-I00, MAT2017- 82970-C2-1-R, and MAT2017-82970-C2-2-R of MINECO, the Fondo Europeo de Desarrollo Regional (FEDER), and the project E13_17R from Aragon Regional Government (Construyendo Europa desde Aragon). P.V. acknowledges support from the ERC starting Grant 758794 "Q-ROOT". ; Peer reviewed

We report the fabrication of epitaxial Y3Fe5O12 (YIG) thin films on Gd3Ga5O12 (111) using a chemical solution method. Cubic YIG is a ferrimagnetic material at room temperature, with excellent magneto-optical properties, high electrical resistivity, and a very narrow ferromagnetic resonance, which makes it particularly suitable for applications in filters and resonators at microwave frequencies. But these properties depend on the precise stoichiometry and distribution of Fe3+ ions among the octahedral/tetrahedral sites of a complex structure, which hampered the production of high-quality YIG thin films by affordable chemical methods. Here we report the chemical solution synthesis of YIG thin films, with excellent chemical, crystalline, and magnetic homogeneity. The films show a very narrow ferromagnetic resonance (long spin relaxation time), comparable to that obtained from high-vacuum physical deposition methods. These results demonstrate that chemical methods can compete to develop nanometer-thick YIG films with the quality required for spintronic devices and other high-frequency applications. ; This work was supported by the Ministry of Science of Spain (Projects No. MAT2016-80762-R, MAT2017-82970-C2-R, and No. MAT2014-51982-C2), the Consellería de Cultura, Educación e Ordenación Universitaria, Xunta de Galicia (ED431F 2016/008, and Centro Singular de Investigación de Galicia Accreditation 2016–2019, ED431G/09), the European Regional Development Fund (ERDF), and the Aragón Regional Government through Projects E26. The microscopy works have been conducted in the Laboratorio de Microscopías Avanzadas (LMA) at Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza. The authors acknowledge the LMA-INA for offering access to their instruments and expertise. Pilar Jiménez-Cavero acknowledges Spanish MECD for support through FPU program (Reference No. FPU014/02546). ; Peer reviewed

3 páginas, 3 figuras.-- et al. ; We study the electrical resistivity of individual Bi nanowires of diameter 100 nm fabricated by electrodeposition using a four-probe method in the temperature range 5–300 K with magnetic fields up to 90 kOe. Low-resistance Ohmic contacts to individual Bi nanowires are achieved using a focused ion beam to deposit W-based nanocontacts. Magnetoresistance measurements show evidence for weak antilocalization at temperatures below 10 K, with a phase-breaking length of 100 nm. ; This work was supported by Spanish Ministry of Science (through Project Nos. MAT2007-65965-C02-02 and MAT2008-06567-C02) including FEDER funding and the Aragon Regional Government. N. Marcano and S. Sangiao acknowledge financial support from Spanish CSIC (JAE-doc program) and Spanish MEC (FPU program). ; Peer reviewed