The dynamic chirality flips of Skyrmion bubbles

Magnetic skyrmion, a topological magnetic domain with complex non-coplanar spin texture, appears a disk-like structure in two dimensions. Exploring three-dimensional spin texture and related chirality switching has drawn enormous interests from the perspective of fundamental research. Here, the three-dimensional magnetic moment of the skyrmion bubbles in centrosymmetric Mn-Ni-Ga were reconstructed with the vector field tomography approach via Lorentz transmission electron microscopy. The type of the bubbles was determined from investigating the magnetic vectors in entire space. We found that the bubbles switched their chirality easily but still keep the polarity to remain the singularity of the bubbles within the material. Our results offer valuable insights into the fundamental mechanisms underlying the spin chirality flips dynamics of skyrmion bubbles.

Nonviral Locally Injected Magnetic Vectors for In Vivo Gene Delivery: A Review of Studies on Magnetofection

Magnetic nanoparticles have been widely used in nanobiomedicine for diagnostics and the treatment of diseases, and as carriers for various drugs. The unique magnetic properties of “magnetic” drugs allow their delivery in a targeted tumor or tissue upon application of a magnetic field. The approach of combining magnetic drug targeting and gene delivery is called magnetofection, and it is very promising. This method is simple and efficient for the delivery of genetic material to cells using magnetic nanoparticles controlled by an external magnetic field. However, magnetofection in vivo has been studied insufficiently both for local and systemic routes of magnetic vector injection, and the relevant data available in the literature are often merely descriptive and contradictory. In this review, we collected and systematized the data on the efficiency of the local injections of magnetic nanoparticles that carry genetic information upon application of external magnetic fields. We also investigated the efficiency of magnetofection in vivo, depending on the structure and coverage of magnetic vectors. The perspectives of the development of the method were also considered.

Paleomagnetism of the Cretaceous Alkaline Magmatism of the Lusitanian Basin, Portugal

<p>The paleogeographic reconstructions of the Iberian plate during the opening of the Atlantic Ocean is still poorly constrained. Major limitations include the paucity of high quality paleomagnetic poles and geochronological constrains, the occurrence of widespread remagnetization events, and controversial seafloor magnetic anomalies. Recent studies provided new high quality paleomagnetic poles from intrusive rocks (sills) dated at 88 and 94 Ma, which contributed to improve the calibration of the apparent polar wander path of Iberia at this time interval. These intrusive rocks are part of the Cretaceous Alkaline Magmatic Pulse that occurred between 72 and 94 Ma, and that is expressed by sills and lava flows cropping out in the Lusitanian Basin of Portugal. Here we provided new paleomagnetic, rock magnetic and anisotropy of magnetic susceptibility (AMS) data of two sills apparently contemporaneous of the Cretaceous Magmatic Alkaline Pulse, namely the Anços sill in the city of Mafra and the Lomba dos Piano sill in the vicinity of the city of Sintra. Rock magnetic experiments consisted in the acquisition and unmixing of isothermal remanent magnetization curves, thermomagnetic analyses, and hysteresis curves, complemented by petrographic analyses. Results indicate that the main magnetic carrier is a mixture of SD to MD titanomagnetite. The magnetic fabric of the Anços sill is oblate in both sills and sub-horizontal k3 eigenvectors indicate that no major titling occurred after the intrusion of the rocks. The Lomba do Piano sill shows more scattered eigenvector directions with a mixture of oblate and prolate fabrics. After alternating field demagnetization, all samples show high-quality and reliable magnetic vectors, with a mean characteristic remanent magnetization orientated Dec=346.88º, I=42.66º (n/N=219/228; k=78.19; a95=1.8º) for Anços and Dec=351.12º, I=48.90º (n/N=142/143; k=94.03; a95=1.23º) for Lomba dos Pianos. All magnetic vectors show a normal (positive) polarity, characteristic of the Cretaceous Normal Polarity Superchron. The corresponding virtual geomagnetic poles (VGP) are Plong=212.62º and Plat=72.03º (N=219, K=98.81, A95=0.96º) for the Anços sill and Plong=212.12º and Plat=78.35º (N=142, K=74.22, A95=1.38º) for the Lomba dos Pianos sill. The Anços VGP plots close to the poles of the Paços d’Ilhas (PI, 88 Ma) and Foz da Fonte (FF; 94 Ma) sills previously published. However, the VGP of the Lomba dos Pianos has a distinct and lower paleolatitude, questioning the contribution of paleosecular variations (PSV). We applied the method of the A95 envelope and find that PSV has not been minimized in the studied sills, which can be explained by the rapid cooling of this kind of rocks. We compiled paleomagnetic data of all sills to provide a more robust paleomagnetic pole for the interval of 88-94 Ma.</p><p> </p><p>This work was supported by the project FCT/UIDB/50019/2020 – IDL funded by FCT</p>

Surface Plasmon-Polaritons at the Interface of Magnetoelectric Hyperbolic Metamaterial

In this paper, we investigated the features of plasmon-polaritons excited at the interface of a magnetoelectric hyperbolic metamaterial and a dielectric for the case when the optical axis is arbitrary oriented under the normal to the boundary. Expressions are obtained for the complex electric and magnetic vectors as well as for the decay constants of the fields on both sides of the interface. The possibility is shown and the conditions are determined for localization of plasmon-polariton at the boundary of metamaterial of different types. It is shown that the wave vector of plasmon-polariton has the component oriented perpendicular to the boundary. It is established that for metamaterials of different types changing the orientation of the optical axis one can realize the conditions when the phase velocity of plasmon-polariton is directed from the boundary inside a metamaterial or a dielectric.

Ellipse Coefficient Map-Based Geomagnetic Fingerprint Considering Azimuth Angles

Geomagnetic fingerprint has been actively studied because of the high signal stability and positioning resolution even when the time has elapsed. However, since the measured three-axis geomagnetism signals at one position are irregular according to the change of the azimuth angle, a large-sized database which is stored magnitudes per angles is required for robust and accurate positioning against the change of the azimuth angle. To solve this problem, this paper proposes a novel approach, an elliptic coefficient map based geomagnetic fingerprint. Unlike the general fingerprint, which stores strength or magnitude of the geomagnetism signals depending on the position, the proposed algorithm minimized the size of databased by storing the Ellipse coefficient map through the ellipse equation derived from the characteristics of 2-D magnetic vectors depending on the position. In addition, the curvature bias of ellipse was reduced by applying the normalized linear least-squares method to 2-D geomagnetic characteristics and the positioning accuracy was improved by applying the weighted geomagnetic signal equalization method.

Region-specific magnetic fields structure sea turtle populations

Philopatry and long distance migrations are common in the animal kingdom, of which sea turtles are flagship examples. Recent studies have suggested sea turtles use the Earth’s magnetic field to navigate across ocean basins to return to their natal area, yet the mechanisms underlying this process remain unknown. If true though, the genetic structure at nesting sites should positively correlate with differences in location-specific magnetic vectors within nesting regions. Here, we confirm this working hypothesis but only in certain regions of the world and for all sea turtle species nesting in those regions. Reversely, where no correlations were found between genetic differentiation and geomagnetic vectors, this was the case for all nesting sea turtle species. Our approach hence reveals parallel but not universal use of geomagnetic cues in sea turtles. We describe magneto-sensing regions as characterized by sharp clines of total and vertical field intensity vectors offering the navigation cues that increase philopatric accuracy and promote genetic structuring among sea turtle populations.

Noncollinear Relativistic DFT+U Calculations of Actinide Dioxide Surfaces

A noncollinear relativistic PBEsol+U study of the low-index actinide dioxides (AnO₂, An = U, Np, Pu) surfaces has been conducted. The surface properties of the AnO₂ have been investigated and the importance of the reorientation of magnetic vectors relative to the plane of the surface is highlighted. In collinear nonrelativistic surface models, the orientation of the magnetic moments is often ignored; however, the use of noncollinear relativistic methods is key to the design of reliable computational models. The ionic relaxation of each surface is shown to be confined to the first three monolayers and we have explored the configurations of the terminal oxygen ions on the reconstructed (001) surface. The reconstructed (001) surfaces are ordered as (001)αβ < (001)α < (001)β in terms of energetics. Electrostatic potential isosurface and scanning tunneling microscopy images have also been calculated. By considering the energetics of the low-index AnO₂ surfaces, an octahedral Wulff crystal morphology has been calculated.

Noncollinear Relativistic DFT+U Calculations of Actinide Dioxide Surfaces

A noncollinear relativistic PBEsol+U study of the low-index actinide dioxides (AnO₂, An = U, Np, Pu) surfaces has been conducted. The surface properties of the AnO₂ have been investigated and the importance of the reorientation of magnetic vectors relative to the plane of the surface is highlighted. In collinear nonrelativistic surface models, the orientation of the magnetic moments is often ignored; however, the use of noncollinear relativistic methods is key to the design of reliable computational models. The ionic relaxation of each surface is shown to be confined to the first three monolayers and we have explored the configurations of the terminal oxygen ions on the reconstructed (001) surface. The reconstructed (001) surfaces are ordered as (001)αβ < (001)α < (001)β in terms of energetics. Electrostatic potential isosurface and scanning tunneling microscopy images have also been calculated. By considering the energetics of the low-index AnO₂ surfaces, an octahedral Wulff crystal morphology has been calculated.

A versatile colloidal Janus platform: surface asymmetry control, functionalization, and applications

A versatile colloidal Janus platform with tunable surface asymmetries and functions was achieved and can play multiple roles as Pickering emulsifiers, catalysts and magnetic vectors in wastewater remedy.