MAGNETIC CIRCULAR X-RAY DICHROISM AT PREPEAK OF FE K-EDGE IN FERRIMAGNETIC FE-OXIDES

We propose a mechanism of the magnetic circular X-ray dichroism (MCXD) at the pre-peak of the Fe K-edge in Fe-oxides. It is found that the h ybridization between the 3d state and the 4p state of Fe ions at tetra hedral sites through the ligand 2p state is responsible for the weak e lectric-dipole absorption at the pre-peak while the spin-orbit interac tion and the spin polarization in the 3d state play a crucial role in MCXD. The important effects of the configuration interaction as well a s of the core hole are discussed in connection with the asymmetric dis persion-type MCXD observed in rare-earth iron garnets and magnetites.