On-Chip Planar Metasurfaces for Magnetic Sensors with Greatly Enhanced Sensitivity.

Metamaterials with engineered structures have been extensively investigated for their capability to manipulate optical, acoustic, or thermal waves. In particular, magnetic metamaterials with precise geometry, shape, size and arrangement of their elemental blocks may be used to concentrate, focus, or guide magnetic fields. In this work, we show the potential of using soft-magnetic permalloy (Py) metasurfaces to tailor the physical properties of other magnetic structures at the local scale.

Survival of skyrmions along granular racetracks at room temperature.

Skyrmions can be envisioned as bits of information that can be transported along nanoracetracks. However, temperature, defects, and/or granularity can produce diffusion, pinning, and, in general, modification in their dynamics. These effects may cause undesired errors in information transport.

Accelerating, guiding, and compressing skyrmions by defect rails.

Magnetic skyrmions are promising candidates as information carriers in spintronic devices. The transport of individual skyrmions in a fast and controlled way is a key issue in this field. Here we introduce a platform for accelerating, guiding and compressing skyrmions along predefined paths.

Depairing Current at High Magnetic Fields in Vortex-Free High-Temperature Superconducting Nanowires.

Superconductors are essential in many present and future technologies, from large-scale devices for medical imaging, accelerators, or fusion experiments to ultra-low-power superconducting electronics. However, their potential applicability, and particularly that of high-temperature superconductors (HTS), is severely affected by limited performances at large magnetic fields and high temperatures, where their use is most needed. One of the main reasons for these limitations is the presence of quantized vortices, whose movements result in losses, internal noise, and reduced performances.

Enhancing the sensitivity of magnetic sensors by 3D metamaterial shells.

Magnetic sensors are key elements in our interconnected smart society. Their sensitivity becomes essential for many applications in fields such as biomedicine, computer memories, geophysics, or space exploration. Here we present a universal way of increasing the sensitivity of magnetic sensors by surrounding them with a spherical metamaterial shell with specially designed anisotropic magnetic properties.

Encoding Magnetic States in Monopole-Like Configurations Using Superconducting Dots.

, , are generated by using a completely new and versatile approach based on the combination of superconductivity and magnetism. Robust, stable, and easily controllable complex spin structures are encoded, modified, and annihilated in a continuous magnetic thin film by defining a variety of magnetic states in superconducting dots.

Tunable High-Field Magnetization in Strongly Exchange-Coupled Freestanding Co/CoO Core/Shell Coaxial Nanowires.

The exchange bias properties of Co/CoO coaxial core/shell nanowires were investigated with cooling and applied fields perpendicular to the wire axis. This configuration leads to unexpected exchange-bias effects. First, the magnetization value at high fields is found to depend on the field-cooling conditions.

Quasistatic Metamaterials: Magnetic Coupling Enhancement by Effective Space Cancellation.

A novel and broadly applicable way to increase magnetic coupling between distant circuits in the quasistatic regime is introduced. It is shown how the use of magnetic metamaterials enhances the magnetic coupling between emitting and receiving coils. Results are experimentally demonstrated by measuring a boost on the efficiency of the wireless transmission of power between distant circuits.

Tailoring Staircase-like Hysteresis Loops in Electrodeposited Trisegmented Magnetic Nanowires: a Strategy toward Minimization of Interwire Interactions.

A new strategy to minimize magnetic interactions between nanowires (NWs) dispersed in a fluid is proposed. Such a strategy consists of preparing trisegmented NWs containing two antiparallel ferromagnetic segments with dissimilar coercivity separated by a nonmagnetic spacer. The trisegmented NWs exhibit a staircase-like hysteresis loop with tunable shape that depends on the relative length of the soft- and hard-magnetic segments and the respective values of saturation magnetization.

A Magnetic Wormhole.

Wormholes are fascinating cosmological objects that can connect two distant regions of the universe. Because of their intriguing nature, constructing a wormhole in a lab seems a formidable task. A theoretical proposal by Greenleaf et al.

A new reversal mode in exchange coupled antiferromagnetic/ferromagnetic disks: distorted viscous vortex.

Magnetic vortices have generated intense interest in recent years due to their unique reversal mechanisms, fascinating topological properties, and exciting potential applications. In addition, the exchange coupling of magnetic vortices to antiferromagnets has also been shown to lead to a range of novel phenomena and functionalities. Here we report a new magnetization reversal mode of magnetic vortices in exchange coupled Ir20Mn80/Fe20Ni80 microdots: distorted viscous vortex reversal.

Magnetic energy harvesting and concentration at a distance by transformation optics.

Based on transformation optics, we introduce a magnetic shell with which one can harvest magnetic energy and distribute it as desired in space with unprecedented efficiency at an arbitrary scale. It allows a very large concentration of magnetic energy in a free space region, which can be used for increasing the sensitivity of magnetic sensors, and the transfer of magnetic energy from a source to a given distant point separated by empty space, with possible applications in wireless transmission of energy.

Experimental realization of a magnetic cloak.

Invisibility to electromagnetic fields has become an exciting theoretical possibility. However, the experimental realization of electromagnetic cloaks has only been achieved starting from simplified approaches (for instance, based on ray approximation, canceling only some terms of the scattering fields, or hiding a bulge in a plane instead of an object in free space). Here, we demonstrate, directly from Maxwell equations, that a specially designed cylindrical superconductor-ferromagnetic bilayer can exactly cloak uniform static magnetic fields, and we experimentally confirmed this effect in an actual setup.