29 research outputs found
Ledge-type Co/L10-FePt exchange-coupled composites
No full textFePt-based exchange-coupled composites consisting of a magnetically hard L10-FePt phase exchange-coupled with a soft ferromagnetic material are promising candidates for future ultra-high density (>1 Tbit/in2) perpendicular magnetic recording media, also being of interest for other applications including spin torque oscillators and micro-electro-mechanical systems, among others. In this paper, the effect of the thickness of a soft Co layer (3 < thCo < 20 nm) on the magnetic behavior of ledge-type fcc(100)-Co/L10(001)-FePt composites deposited on an MgO (100) substrate is systematically studied by combining morpho-structural analyses and angular magnetization measurements. Starting from a film consisting of isolated L10(001)-FePt islands, the ledge-type structure was obtained by depositing a Co layer that either covered the FePt islands or filled-up the inter-island region, gradually forming a continuous layer with increasing Co thickness. A perpendicular anisotropy was maintained up to thCo ∼ 9.5 nm and a significant reduction in the coercivity (about 50% for thCo ∼ 3 nm) with the increase in thCo was observed, indicating that, by coupling hard FePt and soft Co phases in a ledge-type configuration, the writability can be greatly improved. Recoil loops' measurements confirmed the exchange-coupled behavior, reinforcing a potential interest in these systems for future magnetic recording media
Solution-processed nanostructured zinc oxide cathode interfacial layers for efficient inverted organic photovoltaics
No full textInverted organic photovoltaic (OPV) cells based on poly(3-hexylthiophene) (P3HT) as an electron donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as an electron acceptor, were fabricated and characterized. To improve the photovoltaic performance, interface control using either dense or nanostructured ZnO films as cathode buffer layers for effective electron transport was demonstrated, while an under-stoichiometric transition metal oxide, such as MoOx, was employed as the anode buffer layer for efficient hole extraction. Incorporation of a nanostructured ZnO interlayer enhanced electron-hole dissociation by enabling a larger interfacial contact with the active layer, that results in increased short-circuit current density (Jsc) and eventually contributing to higher power conversion efficiency (PCE).</p
Magnetic anisotropy phase-graded A1/L10-FePt films on amorphous glass substrates
No full textMagnetic anisotropy phase-graded A1/L10-FePt films deposited on amorphous glass substrates were investigated combining ultra-high resolution electron microscopy and angular-dependent magnetic measurements. A highly textured (001) L10 FePt film was first deposited at the relative low temperature of 625 K using an MgO/Cr underlayer stack, hence a second layer was grown while continuously decreasing the deposition temperature down to a final value ranging from 515 K to 365 K depending on the layer thickness (tg). This procedure leaded to the formation of a phase-graded system consisting of hard and soft magnetic phases separated by a rough nanometer-size interphase boundary, where the magnetic anisotropy gradually changes due to the variation of the relative amount of hard and soft phases across the whole film thickness. Electron microscopy analysis allowed the structure of the samples to be investigated at an atomic level. The A1 and L10-FePt phases were localized inside the film and the orientation relationships between their lattices were determined. The samples show a preferential perpendicular anisotropy up to tg = 15 nm and a significant reduction of the coercive field with the increase of the graded layer thickness (~ 30% for tg = 5 nm), suggesting their potential application as magnetic recording media
Scaling of Hall coefficient in Co-Bi granular thin films
No full textA series of Co-Bi thin films with Co concentrations c=0, 0.05, 0.2, 0.26, 0.3, 0.333, 0.375, 0.545, were grown by magnetron sputtering on Si(100)/SiNX substrates. Resistivity measurements at zero field (ρxx) as a function of temperature-T exhibit an exponential variation with T in the region of 240K<T<300K. The Hall coefficient as a function of Co concentration diverges as log|c-0.3|0.3 for c<0.333, indicating a scaling of RH nearby a percolation threshold pc=0.3. Only after proper scaling of the anomalous Hall coefficient RS the conventional RS∝(ρxx)n dependence can be satisfied
Scaling of Hall coefficient in Co-Bi granular thin films
No full textA series of Co-Bi thin films with Co concentrations c=0, 0.05, 0.2, 0.26, 0.3, 0.333, 0.375, 0.545, were grown by magnetron sputtering on Si(100)/SiNX substrates. Resistivity measurements at zero field (ρxx) as a function of temperature-T exhibit an exponential variation with T in the region of 240K<T<300K. The Hall coefficient as a function of Co concentration diverges as log|c-0.3|0.3 for c<0.333, indicating a scaling of RH nearby a percolation threshold pc=0.3. Only after proper scaling of the anomalous Hall coefficient RS the conventional RS∝(ρxx)n dependence can be satisfied
Vectorial measurements of the angular coercive field
No full textTwo of the most important parameters in magnetic measurements are the coercive field, Hc, and the remanent coercive field, Hr. In this paper we will look at these parameters in relation to vector measurements taken at an angle with the (mean) anisotropy direction. We will show that the definition and interpretation of these parameters should be reconsidered for angular measurements
Initial Stages of Thermally and Hot-Wire Assisted CVD Copper on SiLK (R) and LTO Substrates Activated with Mercaptopropyl Triethoxysilane Self-Assembled Monolayers
No full textThe initial stages of thermal and hot-wire assisted CVD (HWCVD) of copper were studied with atomic force and scanning electron microscopy. The substrates used were Si (100) wafers covered either with low-temperature silicon oxide (LTO) or with SiLK (R) on which self-assembled monolayers (SAMs) of (3-Mercaptopropyl)trimethoxysilane (MPTMS) were applied. CupraSelect (R) (commercial name of hexafluoroacetylacetonate Cu(I) trimethylvinylsilane) was used as precursor and delivered in the reactor with the aid of a direct-liquid injection system. Thermally grown Cu films follow the initial topography of the substrate thus amplifying the roughness of the initial topography. HWCVD yields smoother films because the growth of Cu is due to entire molecules of the precursor, similarly to thermal CVD, and to activated, easily dissociated, species produced near the hot filament in the gas phase. Once trapped on surface irregularities these species probably dissociate and the deposited metal smooth out the surface yielding smoother Cu films
Magnetotransport properties of cobalt-iron pyrite films
No full textIn this study the preparation, magnetic and magnetotransport properties of cobalt-iron pyrite (CO0.5Fe0.5S2) thin films are reported. These materials have been recently proposed as a tunable source of highly spin-polarized electrons. The films have been prepared by thermal-sulfidation Of Co50Fe50 films fabricated by pulsed laser deposition in a sulfur atmosphere at 500 degrees C, at a pressure of 105 Pa for 12 h. The magnetoresistance curves show an extrinsic negative low field part that is related to alignment of the magnetization between neighbouring grains and scales with M-2 as in polycrystalline manganites and it is maximized in thinner films. This is superimposed on a positive, linear high field part. The Hall effect has a strong anomalous contribution typical of ferromagnetic materials. (c) 2007 Elsevier B.V. All rights reserved.Thin Solid Film
