Owen Willans Richardson magnetic moment conservation of angular momentum ferromagnetic materials Wander Johannes de Haas magnetization polarization angular momenta electrons spin momenta strong
In 1908, Owen Willans Richardson predicted that a change in the magnetic moment of a free body will cause this body to rotate. This effect is a consequence of the conservation of angular momentum and is strong enough to be observable in ferromagnetic materials. Einstein and Wander Johannes de Haas published two papers in 1915 claiming the first experimental observation of the effect. Measurements of this kind demonstrate that the phenomenon of magnetization is caused by the alignment (polarization) of the angular momenta of the electrons in the material along the axis of magnetization. These measurements also allow the separation of the two contributions to the magnetization: that which is associated with the spin and with the orbital motion of the electrons.
