NMR/NQR in the antiferromagnetic parent compounds of high-temperature superconductors

Abstract We review nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) experiments performed in La 2 CuO 4 , YBa 2 Cu 3 O 6 , and Ca(Sr)CuO 2 which are the antiferromagnetic parent compounds of some high-temperature superconductors. Both antiferromagnetic and paramagnetic phases are considered. The following topics are discussed: (1) Measurement and calculation of the sublattice magnetization (and hence the magnon excitation spectrum) in these compounds and its critical behavior; (2) low energy excitations in the antiferromagnetic phase of Ca(Sr)CuO 2 ; (3) various crossovers in Ca(Sr)CuO 2 ; (4) bilayer coupling in YBa 2 Cu 3 O 6 .