Generation and Measurement of Magnetic Fields

Abstract

In basic science areas, such as semiconductor physics, superconductivity, structural biology, and chemistry, magnetic fields are used as a powerful tool for analysis of matter because they can change the physical state of a system. In the presence of a magnetic field, the angular momenta (spins), the orbital motion of charged particles, and therefore the energy of the investigated physical system, are altered.Wemust realize, however, that the size of the induced effects are very modest compared to other physical quantities. One Bohr magneton (typical range of atomic magnetic moments) in a magnetic field of 10 tesla (T) (a 10 T field is ∼200,000 times the strength of the earth's magnetic field) has an energy of 0.58 meV, corresponding to a temperature of 6.7 K, a small value in comparison to room temperature. On the other hand, the generation of a magnetic field of 10Talready requires a noticeable engineering effort, with continuous fields of 50 T being the upper limit of what can be achieved today. Pulsed magnetic fields can be generated up to 100 T for durations in the millisecond range, and up to 1000 T on the microsecond time scale. Therefore, experiments must be chosen judiciously. Very often, a low‐noise sample environment, such as low mechanical vibrations, small field fluctuations (in the case of dc fields), and low temperatures are decisive to the success of scientific measurements in magnetic fields.