Abstract
This paper is a short review of magnetic neutron scattering experiments on La
2-
x
(Sr, Ba)
x
CuO
4. Special emphasis is given to measurements of the spin waves using hot-source triple-axis and spallation-source time-of-flight spectroscopies, magnetic fluctuations near the metal-insulator transition. Fermi surface effects and the dramatic impact of superconductivity on the magnetic response function.