Magnetic phase diagram and magnetic pairing in doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">La</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CuO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

We discuss the temperature-concentration phase diagram of doped ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$. The addition of holes introduces a local ferromagnetic exchange coupling between Cu spins. The resulting frustration destroys the 3D N\'eel state characterizing pure ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$, 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.