We fabricated a device that controls the motion of flux quanta in niobium superconducting film grown on an array nanoscale triangular pinning potentials. The controllable rectification vortex is due to asymmetry magnetic centers. reversal direction flow explained by interaction between vortices trapped nanostructures and interstitial vortices. applied field input current strength can tune both polarity magnitude rectified flow. Our ratchet system modeled theoretically, taking interactions...

Vortex pinning in Nb thin films with rectangular submicrometric magnetic dot arrays exhibits interesting effects. Magnetotransport reveals the existence of two regimes that correspond to types resistivity minima different constant field intervals. The relation array lattice parameters indicates a reconfiguration vortex from square is induced artificially by interaction array. transition occurs when elastic energy becomes larger than provided artificial sites. Using this associated dots can...

To develop a full understanding of interactions in nanomagnet arrays is persistent challenge, critically impacting their technological acceptance. This paper reports the experimental, numerical and analytical investigation Co nanoellipses using first-order reversal curve (FORC) technique. A mean-field analysis has revealed physical mechanisms giving rise to all observed features: shift non-interacting FORC-ridge at low-HC end off local coercivity HC axis; stretch high-HC without shifting it...

Magnetic vortex dynamics in lithographically prepared nanodots is currently a subject of intensive research, particularly after recent demonstration that the polarity can be controlled by in-plane magnetic field. This has stimulated proposals nonvolatile random access memories. In this work, we demonstrate triangular offer real alternative where chirality, addition to polarity, controlled. static regime, show chirality tailored applying field, which experimentally imaged means variable-field...

We have prepared regular square arrays of Ni and Ag dots with typical diameter thickness approaching characteristic low-${T}_{c}$ superconducting length scales. The transport properties Nb films, grown on top these dots, were studied in a wide temperature magnetic-field range. act as pinning centers, thereby producing oscillations the field dependence resistance critical current film. periodicity corresponds to matching lattice spacing. Such an oscillatory behavior is absent for nonmagnetic...

A vortex lattice ratchet effect has been investigated in $\mathrm{Nb}$ films grown on arrays of nanometric $\mathrm{Ni}$ triangles, which induce periodic asymmetric pinning potentials. The motion yields a net dc voltage when an ac driving current is applied to the sample and moves through field This studied taking into account array geometry, temperature, number vortices per unit cell array, currents.

The superconducting critical-field behavior of $2H$-Ta${\mathrm{S}}_{2}$ single crystals intercalated with pyridine (PY), methylamine (MeA), dimethylamine (DMA), and ethylenediamine (EDA) has been measured in the field range 0-267 kG. critical fields parallel to layers for PY MeA exhibit all features expected crossover two-dimensional behavior. A strong upward curvature ${H}_{c2\ensuremath{\parallel}}$ vs $T$ is present. temperature-dependent anisotropy,...

Submicrometric magnetic structures have been fabricated by electron-beam lithography on Si substrates. High-quality patterns obtained with typical length scale of the in range 100 nm. The designed geometrical configurations are suitable for investigation their physical properties transport measurements a controlled way. In particular, long chains connected dots useful to analyze magnetization reversal processes, whereas ordered arrays isolated can be used study pinning effects superconducting films.

Pinning interactions between superconducting vortices in Nb and magnetic Ni dots were studied as a function of current temperature to clarify the nature pinning mechanisms. A strong dependence is found for square array dots, with dependent optimum observation periodic pinning, that decreases (1-T/Tc)3/2. This same critical at first matching field rectangular dots. The analysis these results allows narrow possible mechanisms combination two: interaction vortex moment dot proximity effect....

Rectangular pinning arrays of Ni dots define a potential landscape for vortex motion in Nb films. Magnetotransport experiments which two in-plane orthogonal electrical currents are injected simultaneously allow one to select the direction and magnitude Lorentz force on lattice, thus providing angular dependence motion. The background dissipation depends angle at low magnetic fields, is progressively smeared out with increasing field. periodic locks along channeling directions. Because this,...

Rectangular arrays of Ni dots with small interdot separation have been fabricated in superconducting Nb films. The geometry these rectangular defines deep pinning potential channels. Two effects observed. (i) When the vortices move perpendicular to channels (i.e., along long side array) an enhancement background is observed, as predicted by theoretical models. This occurs for all magnetic fields. (ii) A new anisotropic matching effect, which has not theoretically predicted, measured....

A strong upward curvature in ${H}_{c2\ensuremath{\parallel}}$ and a temperature-dependent critical-field anisotropy are observed $2H$-Ta${\mathrm{S}}_{2}$ intercalated with methylamine. This is characteristic of dimensional crossover Josephson-coupled superconducting layers confirmed by dramatic reduction the coherence length perpendicular to layers. Critical fields greater than 213 kG observed.

The magnetization states in Ni triangular dots under an applied magnetic field have been studied using variable-field force microscopy (VF-MFM) imaging. In order to understand their dynamics we performed micromagnetic simulations which are remarkable agreement with the experimental MFM results. nanostructures present vortices as ground move external field. combination of and imaging allows us identify correctly vortex chiralities polarizations. geometry produces improved contrast core....

Multilayers consisting of superconducting niobium nitride alternated with layers insulating aluminum have been fabricated using dc magnetron reactive sputtering. Under the proper conditions NbN can be produced in a (111) orientation and AlN (0001) an in-plane lattice mismatch only 0.27%. Proper preparation target was necessary to ensure uniform deposition. X-ray diffraction transmission electron microscopy verify layered nature these samples. Transport properties are studied as they relate...

We have designed and fabricated a nanodevice exhibiting simultaneously ferromagnetic properties of nanostructures with plasmonic continuous films. Our device consists an array nanomagnets on top film. The patterned magnetic state is single domain well-defined shape anisotropy. Despite the presence media Au film, system exhibits surface plasmon resonance characteristics i.e., propagating plasmon-polaritons.

Fe/Cu superlattices exhibit a structural and magnetic transition with increasing Fe layer thickness, thus the Curie temperature. An enhancement in superconducting temperature is found proximity coupled Nb/[Fe/Cu] layers as thickness increases. These results indicate weakening of effect for material higher temperature, suggest dominant role spin-flip scattering pair breaking processes which give rise to effect.

Epitaxial ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$ thin films, grown by high-pressure dc sputtering, are irradiated with ${\mathrm{He}}^{+}$ ions at 80 keV doses between ${10}^{14}$ and ${10}^{15} {\mathrm{cm}}^{\ensuremath{-}2}.$ Irradiation reduces the critical temperature but it does not modify carrier concentration. Angle-dependent resistivity is used to show that mass anisotropy change upon irradiation. The melting transition in magnetic fields applied parallel c axis...

We have analyzed kinetic roughening in Fe-Cr superlattices by energy-filtered transmission electron microscopy. The direct access to individual interfaces provides both static and dynamic roughness exponents. find an anomalous non-self-affine scaling of the interface with a time dependent local at short length scales. While deposition conditions affect strongly long-range dynamics, short-range exponent remains unchanged. different short- dynamics outline importance interactions roughening.

We have used ultraviolet, x-ray, and inverse-photoemission spectroscopies to characterize the electronic structure of a novel bismuth cuprate compound with an average composition ${\mathrm{Bi}}_{2.5}$${\mathrm{Sr}}_{1.5}$${\mathrm{Ca}}_{1}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{\mathit{y}}$ which becomes superconductor at 84 K. The data indicate that valence band is shifted \ensuremath{\sim}2 eV higher binding energy respect band-structure calculations. This together presence shake-up satellites...

Magnetotransport properties have been used to investigate vortex phases in Nb films with periodic arrays of magnetic pinning centers. This kind samples show a continuous glass transition similar that observed plain films, but the yields different critical exponents and enhanced temperature at matching field.

Triangular arrays of Ni nanotriangles embedded in superconducting Nb films exhibit unexpected dynamical vortex effects. Collective pinning with a lattice configuration different from the expected fundamental triangular "Abrikosov state" is found. The motion which prevails against periodic potential produced by channelling effects between triangles. Interstitial vortices coexisting pinned this asymmetric potential, lead to ratchet reversal, i.e. DC output voltage changes sign amplitude an...