The distinctive features of equilibrium vortex structures in thin films of anisotropic superconductors in tilted magnetic fields are studied for the limits of moderate and strong anisotropy. The energetically favorable shape of isolated vortex lines is found in the framework of two particular models describing these limiting cases: London theory with an anisotropic mass tensor and London-type model for a stack of Josephson-decoupled superconducting layers. The increase of the field tilting is shown to result in qualitative changes in the vortex-vortex interaction potential: the balance between long-range attractive and repulsive forces occurs to be responsible for a formation of a minimum of the interaction potential vs the intervortex distance. This minimum appears to exist only for a certain restricted range of the vortex tilting angles which shrinks with the decrease of the system anisotropy parameter. Tilted vortices with such unusual interaction potential form clusters with the size depending on the field tilting angle and film thickness or/and can arrange into multiquanta flux lattice. The magnetic flux through the unit cells of the corresponding flux line lattices equals to an integer number M of flux quanta. Thus, the increase in the field tilting should be accompanied by the series of the phase transitions between the vortex lattices with different M .PACS numbers:

On the basis of Ginzburg-Landau theory we investigate order-parameter ͑OP͒ nucleation in superconducting films of a finite thickness in the presence of inhomogeneous magnetic fields induced by ferromagnetic nanoparticles. In particular, we consider a generic system, consisting of a small perpendicularly magnetized nanoparticle, placed at a height h above the disk center. We study the oscillatory dependence of the critical temperature T c of the disk on an external magnetic field H, similar to the classical Little-Parks effect ͓Phys. Rev. Lett. 9, 9 ͑1962͔͒. Two OP nucleation regimes have been found: an appearance of superconductivity either near the disk center ͑under the magnetic particle͒ or near the disk edge. Switching between these regimes at varying the external field has been shown to result in an abrupt modification of the T c ͑H͒ dependence-both the amplitude and the period of the Little-Parks oscillations become much larger, provided that the OP pattern is localized under the particle and R ӷ h, R is the disk radius. The OP nucleation near the magnetic particle is strongly suppressed by increasing the film thickness. Using both analytical and numerical approaches we have found the range of system parameters that are optimal for the experimental observation of the different regimes of localized superconductivity in this hybrid system.

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