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Arrays of Ni100-xCux nanowires ranging in composition 0⩽x⩽75, diameter from 35 to 80 nm, and length from 150 nm to 28 lm have been fabricated by electrochemical co-deposition of Ni and Cu into self-ordered anodic aluminum oxide membranes. As determined by X-ray diffraction and Transmission Electron Microscopy, the crystalline structure shows fcc cubic symmetry with [111] preferred texture and preferential Ni or Cu lattice depending on the composition. Their magnetic properties such as coercivity and squareness have been determined as a function of composition and geometry in a Vibrating Sample Magnetometer in the temperature range from 10 to 290K for applied magnetic fields parallel and perpendicular to the nanowires axis. Addition of Cu into the NiCu alloy up to 50% enhances both parallel coercivity and squareness. For the higher Cu content, these properties decrease and the magnetization easy axis becomes oriented perpendicular to the wires. In addition, coercivity and squareness increase by decreasing the diameter of nanowires which is ascribed to the increase of shape anisotropy. The temperature dependent measurements reflect a complex behavior of the magnetic anisotropy as a result of energy contributions with different evolution with temperature. [ABSTRACT FROM AUTHOR]

The magneto-optic Kerr effect has been employed to determine the magnetization process and estimate the domain structure of microwires with circular magnetic anisotropy. The diameter of microwires was 8 µm, and pieces 2 cm long were selected for measurements. The analysis of the local surface longitudinal and transverse hysteresis loops has allowed us to deduce a vortex magnetic structure with axial core and circular external shell. Moreover, a bamboo-like surface domain structure is confirmed with wave length of around 10 to 15 µm and alternating chirality in adjacent circular domains. The width of the domain wall is estimated to be less than 3 µm. Finally, closure domain structures with significant helical magnetization component are observed extending up to around 1000 µm from the end of the micro wire. [ABSTRACT FROM AUTHOR]

Faraday rotation measurements have been made in samples composed of γ-Fe2O3 nanoparticles dispersed in a SiO2 matrix. All the samples show the same Fe/Si molar ratio but different diameters of the magnetic nanoparticles. A magneto-optical method to measure the particle size using the Faraday effect is presented. The increase of Faraday rotation with the mean diameter of the γ-Fe2O3 particles can be associated with surface effects. The thickness value of their external layer with disordered spins has been obtained using a simple model and its high value suggests the large influence of the matrix on the magnetic properties of the composite. [ABSTRACT FROM AUTHOR]

The increase of complexity and miniaturizing level of Aerospace platforms make use of commercial off the shelf (COTS) components constitute a plausible alternative to the use of military or rad-tolerant components. In this work, giant magnetoresistance commercial sensors are studied to be used as COTS, the next missions to be launched in the framework of the Spanish National Space Program: OPTOS and SEOSAT. This technology of magnetic sensors is interesting due to their high operating range up to 2 mT and the high temperature dynamic range from -50 up to 150 °C. However, in contrast, it presents high hysteresis and nonlinearity, temperature dependence, and poor repeatability. To improve the hysteretic, nonlinear and nonrepetitive behavior, a method consisting of a combination of reset and biasing has been designed and implemented for the ±75 μT linear region centered around 300–375 μT biasing field. [ABSTRACT FROM AUTHOR]