Nuclear Magnetism in Van Vleck Metals
Hiroumi Ishii;
Progress in the study of nuclear magnetism in Van Vleck metals is reviewed. In this class of rare earth intermetallic compounds, mostly of praseodymium, the 4f electronic moment is quenched by the crystalline field. As a result, a T-independent Van Vleck susceptibility much larger than the Pauli susceptibility of a normal metal is observed. Through hyperfine interaction the nuclear spins feel the enhanced external field induced by the Van Vleck susceptibility. This process brings about the enhanced indirect coupling between the nuclear spins, leading to nuclear magnetic ordering around 1 mK in various substances. A brief description of the early developments is followed by a derivation of the basic formulae which govern the enhanced nuclear magnetism and illustrate how nuclear spins order in Van Vieck paramagnets. A discussion of the properties of several enhanced nuclear magnets, including the most recent developments in the field, serves as an illustration of the diversity of nuclear magnetism. The article concludes with a discussion of interaction between the conduction electrons and the nuclear spins. PACS numbers: 71.20 Eh, 71.70 Jp, 75.30 Et, 75.3OKz.
