Coupling efficiency for phase locking of a spin transfer oscillator to a microwave current

The phase locking behavior of spin transfer nano-oscillators (STNOs) to an external microwave signal is experimentally studied as a function of the STNO intrinsic parameters. We extract the coupling strength from our data using the derived phase dynamics of a forced STNO. The predicted trends on the coupling strength for phase locking as a function of intrinsic features of the oscillators i.e. power, linewidth, agility in current, are central to optimize the emitted power in arrays of mutually coupled STNOs

Effect of Crystallographic Texture on Magnetic Characteristics of Cobalt Nanowires

Cobalt nanowires with controlled diameters have been synthesized using electrochemical deposition in etched ion-track polycarbonate membranes. Structural characterization of these nanowires with diameter 70, 90, 120 nm and length 30 μm was performed by scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction techniques. The as-prepared wires show uniform diameter along the whole length and X-ray diffraction analysis reveals that [002] texture of these wires become more pronounced as diameter is reduced. Magnetic characterization of the nanowires shows a clear difference of squareness and coercivity between parallel and perpendicular orientations of the wires with respect to the applied field direction. In case of parallel applied field, the coercivity has been found to be decreasing with increasing diameter of the wires while in perpendicular case; the coercivity observes lower values for larger diameter. The results are explained by taking into account the magnetocrystalline and shape anisotropies with respect to the applied field and domain transformation mechanism when single domain limit is surpassed

What static and dynamic properties should slalom skis possess? Judgments by advanced and expert skiers

Flexural and torsional rigidity are important properties of skis. However, the flexural and torsional rigidity that lead to optimal performance remain to be established. In the present study, four pairs of slalom skis that differed in flexural and torsional rigidity were tested by advanced and expert skiers. Using a 10-item questionnaire, different aspects of the skis’ performance were rated on a 9-point scale. For each pair of skis, physical measurements were compared with the ratings of the two groups of skiers. Correlations (Spearman) were then determined between (i) different mechanical properties of the skis (static and dynamic), (ii) subjective assessments of the participants, and (iii) properties of the skis and the participants’ assessments. The latter showed that expert skiers rate the aspects of the skis more accurately than advanced skiers. Importantly, expert skiers are particularly sensitive to torsion of the skis. These results suggest that such highly rated elements should be addressed in future ski designs

Uniaxial Magnetization Performance of Textured Fe Nanowire Arrays Electrodeposited by a Pulsed Potential Deposition Technique

Textured ferromagnetic Fe nanowire arrays were electrodeposited using a rectangular-pulsed potential deposition technique into anodized aluminum oxide nanochannels. During the electrodeposition of Fe nanowire arrays at a cathodic potential of ??1.2 V, the growth rate of the nanowires was ca. 200 nm s?1. The aspect ratio of Fe nanowires with a diameter of 30?±?5 nm reached ca. 2000. The long axis of Fe nanowires corresponded with the direction when a large overpotential during the on-time pulse was applied, whereas it orientated to the direction under the potentiostatic condition with a small overpotential. By shifting the on-time cathode potential up to ??1.8 V, the texture coefficient for the (200) plane, TC200, reached up to 1.94. Perpendicular magnetization performance was observed in Fe nanowire arrays. With increasing TC200, the squareness of Fe nanowire arrays increased up to 0.95 with the coercivity maintained at 1.4 kOe at room temperature. This research result has opened a novel possibility of Fe nanowire arrays that can be applied for a new permanent magnetic material without rare-earth metals

Configurable multiband microwave absorption states prepared by field cycling in arrays of magnetic nanowires

Arrays of low diameter bi-stable electrodeposited magnetic nanowires demagnetized in the direction parallel to the wires are used to prepare non-saturated stable magnetic states formed by groups of wires magnetized positive and negative with respect to the applied field. Exploiting the coercive field distribution, both the number of wires in each group as well as the number of different groups can be varied by changing the demagnetizing cycle parameters. The ferromagnetic resonance field and peak intensity are shown to be different for each of these magnetic states. By applying demagnetizing cycles, it is possible to induce multiple absorption peaks, and thus show field-programmable multiband absorption properties

Application of the anisotropy field distribution method to arrays of magnetic nanowires

The applicability of the anisotropy field distribution method and the conditions required for an accurate determination of the effective anisotropy field in arrays of magnetic nanowires have been evaluated. In arrays of magnetic nanowires that behave as ideal uniaxial systems having only magnetostatic contributions to the effective anisotropy field, i.e., shape anisotropy and magnetostatic coupling, the method yields accurate values of the average anisotropy field at low-moderate dipolar coupling and accuracy decreases as wire packing increases. When an additional non-negligible magnetocrystalline anisotropy is present, the method is less accurate, as shown for the case of hcp Co nanowires

Ferromagnetic nanowire-loaded membranes for microwave electronics

In this article, we show how the microwave properties of ferromagnetic nanowires electrodeposited into a porous polymer template depend on various parameters such as the geometrical parameters of the nanowires array and elaboration conditions. Our nanowires behave as strong uniaxial nanomagnets and exhibit zero-field resonance frequencies tunable up to 36 GHz. Novel microwave devices such as circulators and filters, using a porous polymer template loaded with metallic nanowires, are discussed. An accurate knowledge of magnetic and dielectric properties of the loaded polymer template is mandatory for the design of such devices. (C) 2008 Elsevier B.V. All rights reserved