A comprehensive collection of papers on theoretical aspects of electronic processes in simple and synthetic metals, superconductors, bulk and low-dimensional semiconductors under extreme conditions, such as high magnetic and electric fields, low and ultra-low temperatures. The main emphasis is on low-dimensional conductors and superconductors, where correlated electrons, interacting with magnetic or nonmagnetic impurities, phonons, photons, or nuclear spins, result in a variety of new physical phenomena, such as quantum oscillations in the superconducting state, Condon instability, Skyrmions and composite fermions in quantum Hall effect systems, and hyperfine field-induced mesoscopic and nanoscopic phenomena. Several new experimental achievements are reported that promise to delineate future trends in low temperature and high magnetic field physics, including the experimental observation of the interplay between superconductivity and nuclear spin ordering at ultra-low temperatures, new observations of Condon domains in normal metals, and an experimental proposal for the realisation of isotopically engineered, semiconductor-based spin-qubit elements for future quantum computation and communication technology.

Physical Phenomena at High Magnetic Fields IV (PPHMF-IV) was the fourth in the series of conferences sponsored by the National High Magnetic Field Laboratory (NHMFL). The success of PPHMF-I, II and III, held in 1991, 1995 and 1998 respectively, encouraged the organizers to once again bring together experts in scientific research areas where high magnetic fields play an important role, to critically assess the current status of research in these areas, and to discuss promising new directions in science, as well as applications which are in the forefront of these fields.

Physical Phenomena at High Magnetic Fields IV (PPHMF-IV) was the fourth in the series of conferences sponsored by the National High Magnetic Field Laboratory (NHMFL). The success of PPHMF-I, II and III, held in 1991, 1995 and 1998 respectively, encouraged the organizers to once again bring together experts in scientific research areas where high magnetic fields play an important role, to critically assess the current status of research in these areas, and to discuss promising new directions in science, as well as applications which are in the forefront of these fields.

The purpose of the conference was to bring together experts in research areas of science in which high magnetic fields play an important role, to critically assess the current status of research in these areas, and to discuss promising new directions in science, as well as applications which are at the forefront of these fields.The program consisted of talks given by leading experts presenting overviews and critical assessments of certain areas, including semiconductors, the quantum Hall effect, heavy fermions, superconductivity, organic solids, chemical systems, and the generation and use of high magnetic fields in basic and applied research.

The spin degree of freedom is an intrinsically quantum-mechanical phenomenon, leading to both intriguing applications and unsolved fundamental issues (such as "where does the proton spin come from"). The present volume investigates central aspects of modern spin physics in the form of extensive lectures on semiconductor spintronics, the spin-pairing mechanism in high-temperature semiconductors, spin in quantum field theory and the nucleon spin.