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Enhancing the pinning force in high-T_c superconductors can be achieved by externally introduced periodic magnetic dots. We have numerically calculated the interaction between the magnetic dot and the vortex in high-T_c superconductors. The London equation is used to generate two-dimensional vortex lattice. In the matching condition, we calculate the attraction force between the magnetic dots and vortices at various conditions. It is found that the magnitude of the pinning from the dots is compatible with the intrinsic pinning force of YBCO thin film materials.

We have developed a novel technique to fabricate extremely uniform arrays of nano-sized dots. Regular arrays of nanometer-sized metallic dots are obtianed by magnetron sputtering deposition through a nanochannel glass replica mask. The platinum replica masks are fabricated using thin film deposition on an etched nanochannel glass and contain hexagonally patterned uniform voids with diameters as small as 50 nanometers. The metallic dot density can be as high as 5×10¹¹ per square centimeter. The magnetic properties of Ni and Co dot arrays have been studied by a Alternating Gradient Magnetometer. The magnetic dot array can be used as pinning centers for superconductors and also can be used as the discrete magnetic media for magnetic recording.

We deal with the problem of nanoscale superconductivity. Nanoscale superconductivity remains to be one of the most interesting research areas in condensed mater. Recent technology and experiments have fabricated high-quality superconducting MgB₂ nanoparticles. We consider the two-band superconductivity in ultrasmall grains, by extending the Richardson exact solution to two-band systems, and develop the theory of interactions between nano-scale ferromagnetic particles and superconductors. The properties of nano-sized two-gap superconductors and the Kondo effect in superconducting ultrasmall grains are investigated as well. The theory of the Josephson effect is presented, and his application to quantum computing are analyzed.

Spin waves (SWs) have been studied experimentally and by simulations in 1000 nm side equilateral triangular Permalloy dots in the Buckle state (B, with in-plane field along the triangle base) and the Y state (Y, with in-plane field perpendicular to the base). The excess of exchange energy at the triangles edges creates channels that allow effective spin wave propagation along the edges in the B state. These quasi one-dimensional SWs emitted by the vertex magnetic charges gradually transform from propagating to standing due to interference and (as pointed out by simulations) are weakly affected by small variations of the aspect ratio (from equilateral to isosceles dots) or by interdot dipolar interaction present in our dot arrays. SWs excited in the Y state have mainly a two-dimensional character. Propagation of the SWs along the edge states in triangular dots opens possibilities for creation of new and versatile spintronic devices.