The effects of geometric confinement on magnetic and superconducting systems

The effects of geometric confinement on magnetic and superconducting systems were studied using magnetic imaging, magnetometry measurements, and transport measurements. The magnetic imaging examined the magnetic domain behavior in evaporated Ni films and wires. Magnetometry measurements, combined with the magnetic imaging, revealed that evaporated Ni films possess perpendicular magnetic anisotropy (PMA) above a certain film thickness. The influence of the sample size on the magnetic domain size and orientation was investigated by using evaporated Ni wires with decreasing width. The preferred orientation of the stripe domains was explained by an existing theoretical model, which considered the free energy of magnetic systems with PMA. Transport measurements were carried out to determine the resistance contribution of the domain walls to the total resistance, taking advantage of the PMA in these evaporated Ni systems.;Transport measurements were carried out on Al wires in order to investigate the resistive processes responsible for the magnetic-field-induced resistance observed in these wires. The physical dimensions of the wires were varied in an attempt to observe the effects of different resistive processes at play. I-V characteristics and magnetoresistance measurements were performed and analyzed. The result strongly supports magnetic flux penetration into the superconducting wires as the source of resistance in these Al wires. However, other resistive processes could not be ruled out.