Nuclear magnetic ordering in metals

Abstract

Spontaneous nuclear magnetic ordering is discussed for the following two groups of metals:1. Metals where the nuclear-electron interaction is so weak that the nuclear spin temperature can be reduced substantially below the electronic and lattice temperatures and where this temperature difference can be kept for a time sufficiently long to perform investigations of the "isolated" nuclear spin system. By this method, nuclear magnetic ordering in Ag and Cu has been observed at nanokelvin nuclear spin temperatures. Here I will also consider the interesting phenomena occurring at negative nuclear spin temperatures.2. Metals where the nuclear-electron coupling is so strong that nuclei and electrons cannot be decoupled for an experimentally relevant time. For these groups of metals the complex NMR spectra of Tl as well as the recent observation of a spontaneous nuclear magnetic ordering transition of In nuclear spins in the cubic intermetallic compound AuIn2 at microkelvin temperatures will be reviewed.