"Spintronics," in which both the spin and charge of electrons are used for logic and memory operations, promises an alternate route to traditional semiconductor electronics. A complete logic architecture can be constructed, which uses planar magnetic wires that are less than a micrometer in width. Logical NOT, logical AND, signal fan-out, and signal cross-over elements each have a simple geometric design, and they can be integrated together into one circuit. An additional element for data input allows information to be written to domain-wall logic circuits.

As fabrication technology pushes the dimensions of ferromagnetic structures into the nanoscale, understanding the magnetization processes of these structures is of fundamental interest, and key to future applications in hard disk drives, magnetic random access memory and other 'spintronic' devices. Measurements on elongated magnetic nanostructures highlighted the importance of nucleation and propagation of a magnetic boundary, or domain wall, between opposing magnetic domains in the magnetization reversal process. Domain-wall propagation in confined structures is of basic interest and critical to the performance of a recently demonstrated magnetic logic scheme for spintronics. A previous study of a 500-nm-wide NiFe structure obtained very low domain-wall mobility in a three-layer device. Here we report room-temperature measurements of the propagation velocity of a domain wall in a single-layer planar Ni80Fe20 ferromagnetic nanowire 200 nm wide. The wall velocities are extremely high and, importantly, the intrinsic wall mobility is close to that in continuous films, indicating that lateral confinement does not significantly affect the gyromagnetic spin damping parameter to the extreme extent previously suggested. Consequently the prospects for high-speed domain-wall motion in future nanoscale spintronic devices are excellent.

An all-metallic submicrometer device is demonstrated experimentally at room temperature that performs logical NOT operations on magnetic logic signals. When this two-terminal ferromagnetic structure is incorporated into a magnetic feedback loop, the junction performs a frequency division operation on an applied oscillating magnetic field. Up to 11 of these junctions are then directly linked together to create a magnetic shift register.

We demonstrate movement of a head-to-head domain wall through a magnetic nanowire simply by passing an electrical current through the domain wall and without any external magnetic field applied. The effect depends on the sense and magnitude of the electrical current and allows direct propagation of domain walls through complex nanowire shapes, contrary to the case of magnetic field induced propagation. The efficiency of this mechanism has been evaluated and the effective force acting on the wall has been found equal to 0.88x10 -9 N.A -1 .Controlling magnetization directly with an electric current rather than a magnetic field is one of the recent exciting developments within spintronics. The main expectations are a very fast reversal of magnetization (< 100 ps) and the ability to control individual magnetic elements without affecting neighbouring structures. In ferromagnetic/nonmagnetic/ferromagnetic multilayer structures, several experiments have demonstrated magnetization reversal of one layer purely by applying a pulsed current and without any externally applied magnetic field [1]. This concept could be also very interesting in the framework of recently demonstrated magnetic logic [2], where logic operations are performed by domain wall propagation through ferromagnetic nanowire junctions, resulting in magnetization reversal. Until now, this propagation has been induced by an external applied field. A potential alternative is current-induced dragging of a domainwall, which does not rely on a generated magnetic field and is now well known in quasiinfinite thin film [3,4]. However, the effect of nanopatterning has never been studied, despite introducing several new conditions and raising important questions. First, the shape anisotropy of certain nanowires (e.g. 5 nm thick, 100 -200 nm wide permalloy) dictates that its magnetization is parallel to the wire axis, and domain walls become headto-head rather than the Bloch walls studied previously. Second, the profile of the domain wall is modified; its width has been shown to be much smaller in nanostructures [5].Third, the edge roughness of nanowires could become very important, possibly severely impairing domain wall propagation. Fourth, can domain walls propagate through nanowires that are not straight?Here, we address these questions and demonstrate experimentally that domain walls can be moved through magnetic nanowire circuits and even around corners by spin

We have found that almost all paper documents, plastic cards and product packaging contain a unique physical identity code formed from microscopic imperfections in the surface. This covert 'fingerprint' is intrinsic and virtually impossible to modify controllably. It can be rapidly read using a low-cost portable laser scanner. Most forms of document and branded-product fraud could be rendered obsolete by use of this code.

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We report on domain wall pinning behavior and the potential-energy landscapes created by notches of two different geometries in planar Permalloy nanowires. Domain wall depinning was probed experimentally using spatially resolved magneto-optical Kerr effect measurements. The spin structure of pinned domain walls was determined using Lorentz microscopy, and domain wall pinning behavior was also analyzed using micromagnetic simulations, which are in good qualitative agreement with experimental results. All notch structures have dimensions that are comparable with the domain wall length scales. For the notch structures investigated, the depinning field experienced by a domain wall is found to be relatively insensitive to notch geometry although the pinning behavior is highly sensitive to both the wall type and the wall chirality spin structure. Energetically, the notches present both potential barriers and/or potential wells depending on the micromagnetic structure of the domain wall, and we find that the chirality of the domain wall is a key determinant of the pinning potential landscape. The pinning behavior of domain walls is discussed in detail, and direct quantitative measurements of the width and depth of the potential wells and/or barriers responsible for domain wall pinning are given for vortex walls pinned in triangular and rectangular notches.

We demonstrate that positively and negatively field-shifted magnetic hysteresis loops can be obtained from a single continuous L-shaped magnetic nanostructure. This is achieved by controlling the coercivity of one arm of the L-shape structure with the magnetization direction of the orthogonal arm. Furthermore, a memory effect is demonstrated by reversing the magnetization direction of one arm while leaving the other unchanged. Good discrimination between the different switching field magnitudes and the ease of fabrication make these continuous magnetic structures more suitable than chains of discrete magnetic dots for performing logical operations.

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.