A quantum-mechanical effect in which the ratio of the magnetization of a solid to the strength of an external magnetic field oscillates as the strength of the magnetic field increases. This effect occurs at low temperatures with very strong magnetic fields. It was discovered by the Dutch physicists Wander Johannes de Haas and Pieter van Alphen in 1930, having been predicted theoretically by Lev Landau in the same year. The de Haas–van Alphen effect has been used very extensively to investigate the Fermi surface.