Magnetism

Magnetism is basically a solid state effect. Liquids and gases are not magnetic and of the elements only the 3d-transition metals iron, cobalt and nickel and the lanthanoid gadolinium are magnetic. However, other transition metals play important roles in magnetic compounds or show ferro-magnetic behaviour in thin layers. The 3d-shells of the 3d-transition metals and the 4f-shells of the lanthanoids are not strongly pertubated by the interatomic binding. Hence some of their atomic properties can be understood using atomic models.

The origin of magnetism can be devided into spin magnetism and orbital magnetism. The states of outer shell electrons of most atoms can be well understood within the Russel-Saunders coupling, also known as spin-orbit coupling or LS-coupling. In this coupling scheme the electronic states can be descibed by the quantum numbers S, m_S, L, m_L, J and m_J. The quantum numbers S and m_S describe the square of the total spin momentum and its orientation into the z-axis. The eigenvalues of the spin operators S² and S_z are S(S+1) and m_S. The quantum numbers L and m_L describe the eigenvalues L(L+1) and m_L of the spatial angular momentum operators L² and L_z. The quantum numbers J and m_J describe the total angular momentum J=L+S.

Of special interest for the atomic origin of magnetism are the magnetic quantum numbers m_S, m_L and m_J. The influence of spin magnetism and orbital magnetism are discussed on separate pages.

Last modified: 2006-05-12