Static High Magnetic Fields and Materials Science

Abstract

Like temperature or pressure, the magnetic field is one of the important thermodynamic parameters that are used to change the inner energies of materials. Materials are essentially composed of atomic nuclei and electrons, and the properties of a material are mainly characterized by the behavior of electrons. An electron has charge and spin, and any material responds to an applied magnetic field in the first place via the charge and spin of the electrons. Materials can be subdivided into classes according to their reaction to an external stimulus like a magnetic or electric field. For example, regarding the electrical properties, materials are classified into insulators, semiconductors, metals and superconductors; the materials containing free charge carriers respond to a magnetic field due to the Landau energy. From these responses, a wealth of important information on the electronic structure is obtained, among others by means of magneto-transport experiments (including the quantum Hall effect), cyclotron resonance and the de Haas-van Alphen effect. Magnetic materials contain magnetic moments due to electron orbits or spins that can be oriented by an applied magnetic field. In a paramagnet, the magnetic moments are disordered in zero magnetic field; in ferro-, ferri- and antiferromagnets the magnetic moments are aligned by quantum-mechanical interactions. In these materials, a variety of phase transitions can be induced by the applied magnetic field.