Inhomogeneous magnetism induced in a superconductor at superconductor-ferromagnet interface

We study a magnetic proximity effect at superconductor (S) - ferromagnet (F) interface. It is shown that due to an exchange of electrons between the F and S metals ferromagnetic correlations extend into the superconductor, being dependent on interface parameters. We show that ferromagnetic exchange field pair breaking effect leads to a formation of subgap bands in the S layer local density of states, that accommodate only one spin-polarized quasiparticles. Equilibrium magnetization leakage into the S layer as function of SF interface quality and a value of ferromagnetic interaction have also been calculated. We show that a damped-oscillatory behavior versus distance from SF interface is a distinguished feature of the exchange-induced magnetization of the S layer.Comment: 10 pages, 7 Postscript figure

Anomalous Superconducting Properties and Field Induced Magnetism in CeCoIn5

In the heavy fermion superconductor CeCoIn5 (Tc=2.3K) the critical field is large, anisotropic and displays hysteresis. The magnitude of the critical-field anisotropy in the a-c plane can be as large as 70 kOe and depends on orientation. Critical field measurements in the (110) plane suggest 2D superconductivity, whereas conventional effective mass anisotropy is observed in the (100) plane. Two distinct field-induced magnetic phases are observed: Ha appears deep in the superconducting phase, while Hb intersects Hc2 at T=1.4 K and extends well above Tc. These observations suggest the possible realization of a direct transition from ferromagnetism to Fulde-Ferrel-Larkin-Ovchinnikov superconductivity in CeCoIn5.Comment: 4 pages, 3 figure

Anisotropy of magnetoresistance in untwinned YBa₂Cu₃O₇₋δ single crystals

In this work we study an influence of the disorientation angle between direction of constant magnetic field up to 15 kOe and ah-plane α ≡ ∠(H,ab) on the temperature dependences of the excess conductivity in the temperature interval of transition to superconducting state in untwinned YBa₂CU₃O₇₋δ single crystals with a small oxygen hypostoichiometry. At temperature T > Tc, the temperature dependence of the excess para-conductivity is interpreted within the Aslamazov-Larkin theoretical model of the fluctuation conductivity for layered superconductors. The cause of appearances of low temperature "tails" (para-coherent transitions) on the resistive transitions, corresponding to different phase regimes of the vortex-matter state is discussed. Remove selecte

Ferromagnetic resonance investigation of macroscopic arrays of magnetic nanoelements fabricated using polysterene nanosphere lithographic mask technique

A dense plane periodical array of cylindrical magnetic nanodots has been fabricated using a lithographic mask formed by self-organization of polystyrene nanospheres. In this paper, we study collective static and dynamic magnetic behavior of this array. We find that this technique produces samples with reasonably small dispersion of magnetic parameters of individual dots. This is evidenced by magnetometry and well-resolved discrete frequencies of standing spin waves measured with cavity and coplanar-waveguide ferromagnetic resonance. The standing spin wave resonances could be reliably observed in a large range of frequencies (4-15 GHz). However the measured linewidth of resonances is about ten times larger than for unpatterned Permalloy. This may be due to some variation in shape and magnetic parameters from dot to dot resulting in inhomogeneous broadening of the resonance lines

μSR studies of the flux vortex phases in a BEDT-TTF superconductor

μSR has been used to probe the structure and stability of the flux vortex array in the organic superconductor κ-(BEDT-TTF)2Cu(SCN)2. At temperatures below 5 K and fields below 5 mT the internal field distribution is found to closely match that expected for a three dimensional (3D) Abrikosov flux line lattice (FLL). Careful studies in this 3D-FLL regime have enabled an improved measurement of the temperature dependence of the superconducting penetration depth to be made. A linear term is found in the temperature dependence of the penetration depth, suggesting the presence of line nodes in the gap parameter and d-wave pairing

Microscale magneto-elastic composite swimmers at the air-water and water-solid interfaces under a uniaxial field

Peer Reviewe

Motion and mixing for multiple ferromagnetic microswimmers

This paper concerns the interaction of several ferromagnetic microswimmers, their motion and the resulting fluid mixing. Each swimmer consists of two ferromagnetic beads joined by an elastic link, and is driven by an external, time-dependent magnetic field. The external field provides a torque on a swimmer and, together with the varying attraction between the magnetic beads, generates a time-irreversible motion leading to persistent swimming in a low Reynolds number environment. The aim of the present paper is to consider the interactions between several swimmers. A regime is considered in which identical swimmers move in the same overall direction, and their motion is synchronised because of driving by the external field. It is found that two swimmers tend to encircle one another while three undergo more complicated motion that may involve the braiding of swimmer trajectories. By means of approximations it is established that the interaction between pairs of swimmers gives circulatory motion which falls off with an inverse square law and is linked to their overall speed of motion through the fluid. As groups of two or more swimmers move through the fluid they process fluid, leaving behind a trail of fluid that has undergone mixing: this is investigated by following streak lines numerically

Real-space imaging of confined magnetic skyrmion tubes

Magnetic skyrmions are topologically nontrivial particles with a potential application as information elements in future spintronic device architectures. While they are commonly portrayed as two dimensional objects, in reality magnetic skyrmions are thought to exist as elongated, tube-like objects extending through the thickness of the host material. The study of this skyrmion tube state (SkT) is vital for furthering the understanding of skyrmion formation and dynamics for future applications. However, direct experimental imaging of skyrmion tubes has yet to be reported. Here, we demonstrate the real-space observation of skyrmion tubes in a lamella of FeGe using resonant magnetic x-ray imaging and comparative micromagnetic simulations, confirming their extended structure. The formation of these structures at the edge of the sample highlights the importance of confinement and edge effects in the stabilisation of the SkT state, opening the door to further investigations into this unexplored dimension of the skyrmion spin texture