NMR studies of singlet-ground-state rare-earth ions in high-Tc superconductors

Abstract

Many of presently known high-Tc superconductors contain rare-earth (RE) ions with an even number of electrons in an unfilled 4f-shell (Pr3+, Tb3+, Ho3+, Tm3+). If the ground state of 4f-electrons is non-degenerate and separated from excited states by high enough energy intervals, one can observe the so-called "enhanced NMR" of RE nuclei at low temperatures. In the present paper some aspects of the enhanced NMR are analyzed in applications to the crystal and electron structure of high-Tc superconductors. © 1992 Springer.