Measurement of Weak Magnetic Fields By Magnetic Resonance

Abstract

Publisher Summary This chapter discusses measurement of weak magnetic fields by magnetic resonance. The new phenomenon links, accurately and linearly, the value of a field B to a circular frequency ω by introducing a new physical constant, the gyromagnetic ratio: ω = γB, where ω is the angular velocity of precession of the magnetic moment (M) of the specimen around the vector B, and γ characterizes the substance in which the resonance is observed or, eventually and with some minor corrections, the nucleus, the magnetic moment of which is put into resonance. The chapter concentrates on the two types of low-field magnetometers. The characteristics of the natural magnetic fields, which bear on the accuracy of the measurements are discussed. Order of magnitude and main characteristics of natural fields are elaborated. Concepts of prepolarization and free nuclear precession are explained. Principle of superconducting interferometers as magnetometers is also discussed in the chapter.