Magnetic phase diagram and magnetic pairing in doped La2CuO4

We discuss the temperature-concentration phase diagram of doped La₂CuO₄. The addition of holes introduces a local ferromagnetic exchange coupling between Cu spins. The resulting frustration destroys the 3D Néel state characterizing pure La₂CuO₄, and generates a new 3D spin-glass phase. In the paramagnetic phase, strongly correlated Cu spins in the planes are canted by the holes, yielding an oscillating dipole-dipole attraction between holes. The possible relevance to superconductivity is discussed.