Limitations of a simple quantum mechanical model: Magnetic dichroism in a relativistic one-electron atom

The magnetic dichroism, i.e., the difference in the absorption coefficient for right- and left-circularly polarized electromagnetic waves, is a relativistic many-electron effect in a magnetic material. Jenkins and Strange have introduced the most simple and analytically solvable quantum mechanical model which exhibits magnetic dichroism, i.e., the relativistic one-electron atom in an external magnetic field. We have extended this model by considering the 2p-3d transitions and by taking into account the effect of an additional crystal field. The model predicts near-zero dichroism for the 2p _1/2-3d_3/2 transition (L₂-absorption) if the crystal field and the effect of the magnetic field on the core states are neglected, in contrast to the strong dichroism for the L₂-absorption in real materials. The reason for this limitation of the model of Jenkins and Strange is discussed. The j-j mixing of the initial states by the additional crystal field potential has some weak effect on the dichroism.