In this work the interactions between neighboring superconducting thin film and ferromagnetic structures, i.e. superconductor-ferromagnet hybrid systems, were studied. A type-II superconducting thin film (Pb82Bi12), was deposited in close proximity to various ferromagnetic structures. These magnetic structures include: (i) alternating iron-brass shims of 275 mu m period, (ii) an array of 4 mu m wide Co stripes with smaller period (9 mu m), (iii) a square array of 50nm diameter, high aspect ratio (5-7) Ni rods with 250nm period. Measurements of critical transport current (IC), resistance (RH(T)) and second critical field (HC2) are reported. A variety of novel effects (enhancement of (IC) and (HC2), matching field effect, field compensation effect, and large hysteresis) are also reported. Using measurements on thin superconducting films atop a Co stripe array with a 9 mu m period, a superconductor-ferromagnet hybrid device (a mechanical superconducting persistent switch) is proposed. In addition, scanning Hall probe microscopy (SHPM) and other imaging techniques were used to characterize the magnetic properties of the systems mentioned. The SHPM was also used to acquire B-H and M-H curves. An additional sharp magnetic needle and electromagnetic coil assembly intended for micromanipulation of small magnetic particles and individual cells was also characterized.

This dissertation describes experimental studies of how a spatially alternating magnetic field can effectively pin the magnetic flux in a superconducting thin film (Pb 82 Bi18), thereby enhancing the superconductivity. The spatially alternating magnetic field was provided by a periodic array of nano-sized magnetic structures: 300 nm spacing triangular array of cobalt rods with 100 nm diameter and 300 nm height. The superconducting film deposited on top of the magnetic structures, or an embedded Ferromagnet- Superconductor Hybrids (FSH), showed enhanced critical current and critical magnetic field. The embedded FSH also showed the field matching effect, the field compensation effect, and hysteresis. This dissertation also explains how to fabricate and characterize magnetic nano- structures. Electron beam lithography and electroplating method were used to fabricate the magnetic nanostructures. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the structures of the magnetic rods. Magnetic force microscopy (MFM) was used to study their magnetic properties.

Local studies of vortex distribution in superconducting (SC) thin films and their pinning by natural and artificial defects were performed using low-temperature magnetic force microscopy (MFM). The depinning of vortices by the MFM tip was visualized and the local pinning force was estimated in a good agreement with global transport measurements. It was shown that the presence of an ordered array of ferromagnetic dots being in a magnetic vortex state underneath the SC film significantly influences the natural pinning landscape of the superconductor leading to commensurate pinning effects. This strong pinning exceeds the repulsive interaction between the SC vortices and allows vortex clusters to be located at each dot. For industrially applicable YBCO films the main question discussed was a correlation between vortices and artificial defects as well as vortex imaging on rough thin films. Since the surface roughness causes a severe problem to the scanning tip, a nanoscale wedge polishing technique was developed. Mounting the sample under a defined small angle results in a smooth surface and a monotonic thickness reduction of the film along the length of the sample.

A comprehensive collection of overview articles on novel microscopy methods for imaging magnetic structures on the nanoscale. Written by leading scientists in the field, the book covers synchrotron based methods, spin-polarized electron methods, and scanning probe techniques. It constitutes a valuable source of reference for graduate students and newcomers to the field.

The ability to understand and control the unique properties of interfaces has created an entirely new field of magnetism which already has a profound impact in technology and is providing the basis for a revolution in electronics. The last decade has seen dramatic progress in the development of magnetic devices for information technology but also in the basic understanding of the physics of magnetic nanostructures. This volume describes thin film magnetic properties and methods for characterising thin film structure topics that underpin the present 'spintronics' revolution in which devices are based on combined magnetic materials and semiconductors. Volume IV deals with the fundamentals of spintronics: magnetoelectronic materials, spin injection and detection, micromagnetics and the development of magnetic random access memory based on GMR and tunnel junction devices. Together these books provide readers with a comprehensive account of an exciting and rapidly developing field. The treatment is designed to be accessible both to newcomers and to experts already working in this field who would like to get a better understanding of this very diversified area of research.

Magneto-Optical Imaging has developed rapidly over the last decade to emerge as a leading technique to directly visualise the static and dynamic magnetic behaviour of materials, capable of following magnetic processes on the scale of centimeters to sub-microns and at timescales from hours to nanoseconds. The images are direct, real-time, and give space-resolved information, such as ultrafast magnetic processes and revealing the motion of individual vortices in superconductors. The book is a fully up-to-date report of the present status of the technique.