Chapter 21 - Materials in a High Magnetic Field

Abstract

The response of metals, semiconductors, and superconductors to a high magnetic field can reveal many complex quantum mechanical properties of such materials. Traditionally, metals and semiconductors are probed by means of magnetization measurements, magnetotransport measurements, and magnetic resonance to get information on quantum electronic structures through cyclotron resonance, the de Haas–van Alphen effect, the Subnikov–de Haas effect, and the quantum Hall effect. It is now realized that not only does a magnetic field interact with the conduction electrons and magnetic moments in such materials, it can also couple with the structural lattice through magnetoelastic coupling. Thus the uses for high magnetic field nowadays encompass wider subject areas that include: change of the energy level structure of a material and exploration of the excited states, alignment of spins and lifting of frustration in low-dimensional magnets, influence on the character of the quasiparticles in strongly correlated electron metals, dissipationless current-carrying properties of superconductors, and magnetic field–induced phase transition in magnetic and/or charge-ordered systems. The diamagnetic materials also respond to a magnetic field via Larmour diamagnetism, which is caused by the orbital motion of electrons. Biological materials belong to this class, where the effects of the magnetic field are relatively small, roughly three orders of magnitude smaller in comparison with those observed in metallic systems or magnetic materials, but have many interesting implications. This article will present a brief introduction to these subject areas, focusing particularly on two areas of current technological interest, namely, superconductors for high current-carrying applications and multifunctional magnetic materials.